Systematic variation of cyanobuta-1,3-dienes and expanded tetracyanoquinodimethane analogues as electron acceptors in photoactive, rigid porphyrin conjugates

FULL PAPER

DOI: 10.1002/ejoc.201403252

Systematic Variation of Cyanobuta-1,3-dienes and Expanded

Tetracyanoquinodimethane Analogues as Electron Acceptors in Photoactive,

Rigid Porphyrin Conjugates

Lorenz M. Urner,^[a]Michael Sekita,^[b]Nils Trapp,^[a]W. Bernd Schweizer,^[a]

Michael Wörle,^[a]Jean-Paul Gisselbrecht,^[c]Corinne Boudon,^[c]Dirk M. Guldi,*^[b]and

François Diederich*^[a]

Dedicated to Professor Jean-Pierre Sauvage on the occasion of his 70th birthday

Keywords: Energy conversion / Photochemistry / Donor–acceptor systems / Electron transfer / Porphyrinoids

We report on a homologous series of nine electron donor–

acceptor systems featuring push–pull chromophores as elec- vs. Fc⁺/Fc. Characterization of the conjugates includes X-ray

tron acceptors, which are accessible by a cycloaddition-retro- crystallography, electrochemistry, DFT calculations, and fluo-

electrocyclization (CA-RE) reaction. The conjugates com- rescence spectroscopy. The extent of Zn^IIporphyrin fluores-

with first reduction potentials ranging from –1.78 to –0.58 V

prise a Zn^IIporphyrin as electron donor, which is connected

through either rigid phenylene-ethynylene-phenylene

(PEP)-bicyclo[2.2.2]octane or a PEP-trans-decahydroquino-

cence quenching correlates with the strength of the electron

acceptor. Overall, we demonstrate the synthetic feasibility of

rationally modulating the acceptor strength by means of the

a

line spacer to different anilino-substituted multicyanobuta- CA-RE reaction in geometrically well-defined electron do-

dienes or extended tetracyanoquinodimethane analogues

nor–acceptor conjugates.

Over the past decade, we have established a library of

around 300 electroactive molecular materials, encompassing

diverse acetylene-derived conjugated, planar, and non-

planar organic acceptors.^[6]Of particular interest are the

nonplanar acetylene-derived push–pull chromophores that

are made by the cycloaddition-retroelectrocyclization (CA-

RE) reaction between electronically-activated alkynes and

electron-deficient olefins, such as tetracyanoethylene

(TCNE), tetracyanoquinodimethane (TCNQ), tri- and di-

cyanovinyls.^[7–9]This reaction paves the regioselective way

towards tunable electron acceptors with first reduction po-

tentials of up to +0.16 V vs. the ferrocenium/ferrocene cou-

ple (Fc⁺/Fc) in CH₂Cl₂. Many of the CA-RE products fea-

ture interesting physical properties, such as intense low-en-

ergy intramolecular charge-transfer absorptions, high solu-

bility resulting from their nonplanarity, high third-order

optical nonlinearities, and high thermal stability.^[10]To this

Introduction

Organic solar cells represent a promising technology^[1]

that is expected to provide a renewable and inexpensive way

to help meet one of the great challenges of this century, that

is, energy supply for our society.^[2]Yet, to move towards

the cost-effective use of solar energy, improving the power

conversion efficiency is crucial.^[3]Given that the current

structure space of available electron acceptors (n-type) is

fairly limited,^[4]reaching better device performances could

be enabled through the identification and the evaluation of

novel molecular n-type materials as viable alternatives to

fullerene- and/or rylene-based electron acceptors.^[5]

[a] Laboratorium für Organische Chemie, ETH Zürich,

Vladimir-Prelog-Weg 3, 8093 Zürich, Switzerland

E-mail: diederich@org.chem.ethz.ch

http://ww w .diederich.chem.ethz.ch

[b] Department of Chemistry and Pharmacy and Interdisciplinary end, the aforementioned limitations regarding the diversity

Center for Molecular Materials, Friedrich-Alexander-

Universität Erlangen-Nürnberg,

of n-type acceptor materials triggered our interests in the

performance of nonplanar, tunable acceptors, prepared by

the CA-RE reaction, in photoactive molecular materials. A

first step towards this goal was their successful integration

into a “molecular heterojunction”, namely a zinc(II) por-

phyrin electron donor covalently linked to an anilino-sub-

stituted tetracyanobuta-1,3-diene electron acceptor.^[11]This

system underwent photoinduced electron transfer from the

Egerlandstrasse 3, 91058 Erlangen, Germany

https://ww w .chemie.uni-erlangen.de/dcp/department/visitenk-

arten/dirk-guldi/

[c] Laboratoire d’Electrochimie et de Chimie Physique du Corps

Solide, Institute de Chimie-UMR 7177, CNRS, Université de

Strasbourg,

4, rue Blaise Pascal, CS 90032, 67081 Strasbourg Cedex, France

Supporting information for this article is available on the

WWW under http://dx.doi.org/10.1002/ejoc.201403252.

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porphyrin donor to the multicyanobuta-1,3-diene acceptor, underlying Gibbs free energy to be assessed in the form of

generating a long-lived charge-separated state with a life- a Marcus curve.^[12]As very strong electron acceptors with

time of 2.3 μs in PhCN. To further explore the structural first reduction potentials of up to +0.16 V, comparable to

space of potentially photoactive push–pull chromophores the first reduction potential of F₄-TCNQ, are accessible by

and to examine the versatility of the CA-RE reaction in the CA-RE reaction,^[13]photoinduced electron transfer oc-

complex molecular systems, we prepared a homologous curring far in the inverted region should be feasible – a

series of covalently linked multicomponent electron donor– property not fully realized in previous series of electron do-

acceptor conjugates. The electron acceptors were rationally nor–acceptor conjugates.^[14]

chosen from our library to cover a broad range of first re-

Herein, we report on the synthesis, electrochemical, and

duction potentials. Eventually, such a series of related cova- preliminary photophysical properties of nine conjugates 1 –

lent multicomponent systems would enable the relationship (Ϯ)-9, and their corresponding references 10 – (Ϯ)-19 (Fig-

between the rate of photoinduced electron transfer and the ure 1). The conjugates feature a meso-tetraarylzinc(II)

Figure 1. (a) A series of electron donor–acceptor conjugates featuring push–pull chromophores as acceptors. (b) Corresponding reference

compounds; Ar = 3,5-di-tert-butylphenyl.

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Photoactive, Rigid Porphyrin Conjugates

porphyrin (ZnP) as electron donor, two types of long, rigid ene-ethynylene-phenylene (PEP)-bicyclo[2.2.2]octane (S¹)

spacers (S¹and S²), and push–pull acceptors, namely anil- and a PEP-trans-decahydroquinoline (S²), which both com-

ino-substituted extended TCNQs (exTCNQs), 1,1,4,4-tetra- prise a conjugated part (PEP) and, towards the acceptor

cyanobuta-1,3-dienes (TCBDs), 1,1,4-tri-, and 1,1-di- side, a saturated, ananchomeric (i.e., conformationally

cyanobuta-1,3-diene derivatives (DCBDs) as electron ac- locked) part. Such a design should, on the one hand, dimin-

ceptors with first reduction potentials ranging from –1.78 ish the electronic coupling between the porphyrin donor

to –0.58 V. Characterization by X-ray crystallography of and the electron acceptor and thereby promote long-lived

ZnP-S¹-DCBD (5), several building blocks, and reference charge-separated states, and, on the other hand, provide

compounds, complemented by electrochemistry and DFT two different ways of connecting the push–pull chromo-

calculations, provide detailed information on the geometri- phores. In case of linker S¹, the groups are attached to the

cal and electronic factors as a means to dissect the photoin- buta-1,3-diene skeleton, whereas for linker S², they are con-

duced electron transfer processes. Steady-state fluorescence nected through their anilino groups. As a result, linker S²

properties in toluene are reported as a preliminary account would allow a more diverse set of electron acceptors to be

of the overall photophysics. Detailed investigations by time- integrated into the conjugates. The electron acceptors are

resolved spectroscopy and analysis within the framework of push–pull chromophores synthesized by the CA-RE reac-

Marcus theory will be reported in a photophysical follow- tion and were rationally chosen from our library according

up article.

to their first reduction potentials.

To obtain a small library of conjugates with varying ac-

ceptors, we chose a synthetic strategy relying on a modular

building block approach. We envisioned that the individual

electron donor, linker, and acetylenic pre-acceptor building

blocks would be synthesized first, and then assembled on

to the pre-dyads, which were transformed by the CA-RE

reaction as the final step into the functional conjugates. The

building blocks and the key transformations used for their

assembly are illustrated in Scheme 1. We planned to couple

the zinc porphyrin 20 to the linker building blocks 21 or

(Ϯ)-22 by a Sonogashira reaction. Various (alkyne) building

blocks 23–26 could then be attached to these electron do-

nor-linker conjugates to generate a variety of “pre-dyads”.

Depending on the linker type (S¹or S²), these alkyne build-

ing blocks would be coupled through a Sonogashira or Gla-

Results and Discussion

Molecular Design and Synthetic Strategy

The molecular design presented in this work focused on

a structurally rigidified version of our previous photoactive

multicomponent systems.^[11]In the latter, we connected a

zinc porphyrin, meso-substituted with 3,5-di-tert-but-

ylphenyl groups to provide sufficient solubility, to a tetra-

cyano- or pentacyanobuta-1,3-diene electron acceptor

through a flexible linker. To obtain precise control over the

electron donor–acceptor distance and orientation, we iden-

tified two possible new linker structures, namely a phenyl-

Scheme 1. The retrosynthetic strategy of the multicomponent systems, which comprise either linker S¹or S², relies on three key disconnec-

tions (dotted lines/circles), giving rise to a modular synthesis based on the building blocks 20–26. The tetracyanobutadiene acceptor is

drawn as a typical structure for the push–pull chromophores; TMS = trimethylsilyl, Boc = tert-butoxycarbonyl.

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ser-type reaction (in case of S¹), or through a Buchwald– obtained by slow evaporation of a CH₂Cl₂/MeOH solution;

Hartwig amination (in case of S²).

the results of single-crystal X-ray diffraction analysis pro-

In the following paragraphs, the synthesis of 1 – (Ϯ)-9 vided valuable information for the geometrical analysis

and reference ZnP-S (10) is described. The preparation of (Scheme 2, a).

reference compounds 11 – (Ϯ)-19 is reported in the Sup-

porting Information.

The first four synthetic steps towards bicyclo[2.2.2]-

octane building block 21 were performed by following a

reported procedure.^[18]After condensation of p-bromo-

acetophenone with diethyl (ethoxymethylene)malonate

(DEEMM), followed by treatment with acetyl chloride, to

Synthesis of the Building Blocks

For the synthesis of the zinc(II) phorphyrin building give 2-pyrone 30, an inverse-electron-demand Diels–Alder

block 20, we decided to use a statistical MacDonald “2+2” reaction with ethylene gas at high pressure (88 bar) under

approach, due to the A₃B-substitution type and the large extrusion of CO₂gave access to the bicyclo[2.2.2]octene

amounts required (Ͼ 4 g).^[15]Aldehyde 27 (Scheme S1 in scaffold 31 (Scheme 2, b). Purification was only successful

the Supporting Information) was condensed with pyrrole, after hydrogenation over Pt/C to give 32, which spontane-

under InCl₃-catalysis, to afford dipyrromethane 28, which ously crystallized out from the reaction solvent EtOH (for

was isolated by recrystallization from EtOH/H₂O, 4:1 the X-ray structure of 32, see Section S5.10 in the Support-

(Scheme 2, a).^[16]Porphyrin formation was accomplished by ing Information). Saponification to acid 33 was followed by

reacting dipyrromethane 28 with aldehydes 27 and 29,^[17]reduction with BH₃·THF to alcohol 34, which was trans-

using the Lindsey conditions, followed by zinc insertion, formed by a Swern oxidation into aldehyde 35. Given that

and removal of the TMS group to maximally afford 2.5 g aldehyde 35 was sensitive to air oxidation, it was not further

of porphyrin 20 in 10% overall yield per batch (Scheme 2a; purified, but was used directly in the next step, the Best-

the best yield obtained for this reaction was 14%). Crystals mann–Ohira modification of the Seyfert–Gilbert homolo-

of porphyrin 20 that were suitable for X-ray diffraction were gation, using the Bestmann–Ohira reagent 36.^[19]Protection

Scheme 2. Synthesis of the molecular building blocks: (a) zinc porphyrin 20, (b) bicyclo[2.2.2]octane 21, and (c) trans-decahydroquinoline

(Ϯ)-22. Also shown are the X-ray structures of 20·MeOH, 21, and (Ϯ)-45·HCl. Atomic displacement parameters at 100 K are shown at

50% probability level. See Section S5 in the Supporting Information for more information; TFA = trifluoroacetic acid, DDQ = 2,3-

dichloro-5,6-dicyano-1,4-benzoquinone, TBAF = nBu₄NF, DEEMM = diethyl (ethoxymethylene)malonate, DME = 1,2-dimethoxyethane,

DIAD = diisopropyl azodicarboxylate.

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of the resulting alkyne 37 with a TMS group was achieved (Ϯ)-45·HCl confirmed the configurational assignment

in excellent yield by using the procedure developed by Shaw (Scheme 2, c). Finally, amine (Ϯ)-45 was protected with a

and Rahaim.^[20]Overall, the yield of 21 was 11% over eight Boc group to give carbamate (Ϯ)-22 in an overall yield of

steps. The structure of bicyclo[2.2.2]octane building block 7% over nine steps.

21 was confirmed by X-ray diffraction analysis (Scheme 2,

The synthesis of the alkyne pre-acceptor building blocks

b).

24–26 was accomplished by using standard Sonogashira or

The synthesis of trans-decahydroquinoline building block Glaser–Hay coupling procedures and is described in

(Ϯ)-22 started from cyclohexenone, which was subjected to Scheme S2 in the Supporting Information; bromide 23 is

a Cu-catalyzed 1,4-conjugate addition with p-bromophen- commercially available.

ylmagnesium bromide and subsequent enolate trapping

with TMSCl to give TMS enol ether (Ϯ)-38 (Scheme 2,

c).^[21]Allylation to (Ϯ)-39 with allyl iodide and AgOCOCF₃

Assembly of the Building Blocks to the “Pre-Dyads”

proceeded diasteroselectively with a maximum yield of 49%

to give the desired trans-substitution pattern.^[22]After pro-

For the coupling of porphyrin 20 to linker moieties 21

tection of the ketone functionality as dioxolane (Ϯ)-40, and (Ϯ)-22, we chose a Cu-free Sonogashira reaction (Heck

hydroboration of the alkene with Cy₂BH·THF [attempts alkynylation),^[26]because Cu insertion into the porphyrin

with 9-borabicyclo[3.3.1]nonane (9-BBN-H), failed] and has detrimental effects on the photophysical properties^[26]

subsequent oxidation resulted in the formation of primary and because Cu-free Sonogashira-catalyst systems based on

alcohol (Ϯ)-41.^[23]By means of Gabriel synthesis, transfor- [Pd₂(dba)₃]/AsPh₃have been widely applied with por-

mation into phthalimide (Ϯ)-42 by a Mitsunobu reaction, phyrins as coupling partners.^[26,27]We identified suitable re-

and subsequent cleavage with hydrazine led to primary action conditions, which are based on similar methods de-

amine (Ϯ)-43. Cyclization to imine (Ϯ)-44 occurred upon scribed by Lindsey and co-workers,^[28]and by Mårtensson

deprotection of the dioxolane group with HCl.^[24]Re- and co-workers.^[29]The use of [Pd₂(dba)₃] (15 mol-%)/

duction to the trans-decahydroquinoline (Ϯ)-45 had to oc- P(otol)₃(3 equiv.) as catalyst with Et₃N (ca. 120 equiv.) as

cur diastereoselectively. By following a reported synthesis, base in 1,2-dichloroethane/EtOH (1:1; ca. 4 mm) at 80 °C

using NaBH₃CN, a disappointing cis/trans ratio of 42:58 for 24 h resulted in reliable yields of approximately 40%

was determined (¹H NMR analysis; Table S1, entry 9).^[24](based on alkynyl-porphyrin 20 and at a 2 mmol scale)

A screening of reducing agents, solvents, and temperatures when applied to the coupling of 20 with the linker building

revealed that the use of LiBH₄in THF at –78 °C resulted blocks 21, (Ϯ)-22, or 46 (Scheme 3). Commercially available

in the highest diastereoselective induction, with a cis/trans bromide 46 was used to prepare the reference ZnP-linker

ratio of 20:80 (Table S1, entry 1), which is a result that is compound ZnP-S 10 (S: reference spacer).

consistent with the preference of small nucleophiles for ax-

Purification by size-exclusion chromatography turned

ial attack according to Cieplak’s model.^[25]The diastereo- out to be necessary only for apolar ZnP-S (10), whereas

isomers were separated by recrystallization of the HCl salt porphyrin-linker conjugates 47 and (Ϯ)-48 were pure after

from EtOAc/MeOH (5:4). An X-ray crystal structure of silica gel chromatography as proven by elemental analysis

Scheme 3. Assembly of the molecular building blocks to the “pre-dyads” 50, 51, (Ϯ)-54, and (Ϯ)-55, and reference ZnP-S 10.

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Figure 2. (a) X-ray crystal structure of dimeric (Ϯ)-55 at 100 K with atomic displacement parameters drawn at 50% probability level. H-

atoms and tBu groups are omitted for clarity. Three or four disordered CH₂Cl₂(individual sites could not be identified due to extremely

diffuse density) were removed from the data by using the SQUEEZE procedure.^[32]Color code: grey C, blue N, steel blue Zn. (b) Packing

of dimeric (Ϯ)-55 along the crystallographic a- and b-axes, thereby forming a microporous network along this plane. (c) Lateral intercal-

ation of columns of dimeric (Ϯ)-55 along the crystallographic c-axis showing channels of 8.0 Å by 6.6 Å between the columns (van der

Waals spheres shown at 0.7 of atomic radii).

and high-resolution MALDI mass spectrometry. However, [Pd₂(dba)₃]/SPhos, proceeded in 79% yield (see Scheme S2

it should be noted that for porphyrin (Ϯ)-48 an additional in the Supporting Information). Despite being a tedious

purification was necessary to remove the palladium ligand and low-yielding method, BHA nonetheless worked reliably

dibenzylideneacetone (dba), which interestingly seemed to for preparing (Ϯ)-54 and (Ϯ)-55.

bind preferentially to the decahydroquinolyl-substituted

porphyrin. Dba was removed by precipitation from EtOH, (Ϯ)-55 with a terminal DMA-buta-1,3-diynyl residue (Fig-

in which only dba is soluble, but not the porphyrin. ure 2, a). The compound forms a macrocyclic dimer of

An X-ray crystal structure was obtained for porphyrin

Deprotection of porphyrin 47 with tetrabutylammonium molecular weight 2990.64 gmol^–1, through coordination of

fluoride (TBAF) gave terminal alkyne 49, which was trans- the terminal DMA nitrogen atoms to the porphyrin-bound

formed into “pre-dyads” 50 and 51. Sonogashira coupling zinc(II) ions. Crystallization as a supramolecular dimer was

of porphyrin 49 with bromide 23 resulted in the DMA-eth- probably facilitated as a result of the ideal structural dimen-

ynyl-appended porphyrin 50 (in this case, only the condi- sions of the linker, because crystallization attempts of (Ϯ)-

tions by Lindsey and co-workers {[Pd₂(dba)₃]/P(otol)₃in 54, for example, did not lead to X-ray quality crystals. The

toluene/Et₃N, 5:1}, under microwave heating, were effec- difference might be the additional flexibility imparted by

tive).^[28]Glaser-type coupling of porphyrin 49 with alkyne the buta-1,3-diynediyl moiety in the linker of (Ϯ)-55 as

24 afforded DMA-butadiynyl-appended porphyrin 51 compared to the ethynediyl linker in (Ϯ)-54. In fact, angle

(Scheme 3);^[30]DMA = dimethylanilino.

bending occurs at all four C_sp-atoms in the extended spacer,

Mild, non-acidic deprotection of (Ϯ)-48 afforded deca- with C–CϵC angles between 175.4(6) and 178.3(3)°. The

hydroquinolyl-substituted zinc porphyrin (Ϯ)-52,^[31]which greater stiffness of the ethynediyl spacer in the tolane moi-

we intended to couple to the acetylenic pre-acceptor build- ety of (Ϯ)-55 is reflected by smaller C–CϵC angle bending

ing blocks 25 and 26 by a Buchwald–Hartwig amination of 178.2(8) and 178.6(6)°. In addition, oligomerization of

(BHA). However, decahydroquinoline is a strong ligand for (Ϯ)-55 up to the pentamer was observed by HRMS

the zinc porphyrin and the inherent self-complementarity (MALDI) in the high molecular weight region (Figure S1

of (Ϯ)-52 led to self-assembly and rendered it completely in the Supporting Information). The meso-porphyrin di-

insoluble in organic solvents. It could only be dissolved in mers pack along the crystallographic a- and b-axes, forming

organic solvents by adding 20 vol.-% pyridine, which dis- a network of microporous channels (Figure 2, b and c). The

rupts the self-association. Therefore, porphyrin (Ϯ)-52 was columns of porphyrin dimers, between which these channels

demetallated with trifluoroacetic acid (TFA) to the readily are formed, laterally intercalate along the crystallographic

soluble free-base porphyrin (Ϯ)-53. BHA with bromides 25 c-axis (Figure 2, c).

and 26 was achieved with [Pd₂dba₃]/SPhos, NaOtBu, in tol-

uene at 140 °C under microwave irradiation for 2.5 h. How-

ever, the yields of “pre-dyads” (Ϯ)-54 and (Ϯ)-55 after zinc

reinsertion were very low, 14 and 7%, respectively, and the

compounds were only obtained after a tedious purification,

Synthesis of the Functional Electron Donor–Acceptor

Conjugates by the CA-RE Reaction

required to remove the small amounts of palladium inserted

CA-RE reaction of porphyrins 50 and 51 with TCNQ,

into the free-base porphyrins. In comparison, the BHA of under common reaction conditions (toluene, 80 °C,

decahydroquinoline with 25 or 26 using the same catalyst, 24 h),^[33]afforded the electron donor–acceptor conjugates

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Photoactive, Rigid Porphyrin Conjugates

bearing extended TCNQ acceptors ZnP-S¹-exTCNQ 1 and

Conjugates 6–8 were isolated as interconverting diaste-

2 (Scheme 4). Addition of TCNE to the “pre-dyads” 50, reoisomeric Z/E-mixtures with ratios of 2:1, 7:3, and 1:10,

51, and (Ϯ)-54, using common conditions (CH₂Cl₂, 23 °C, respectively (Scheme 4). They were characterized as diaste-

4 h),^[34]gave the dyads with tetracyanobuta-1,3-diene ac- reoisomeric mixtures, including assignment of the ¹³C

ceptors ZnP-S¹-TCBD 3, 4, and ZnP-S²-TCBD (Ϯ)-9, NMR peaks, by comparison to the corresponding refer-

respectively. For the latter, an additional zinc re-metallation ences 16–18, which could be isolated as separate diastereo-

step was necessary because HRMS (MALDI) indicated isomers in the case of 16 and 17. The configurational as-

partial loss of the zinc ion, which might be attributed to the signment was confirmed by the X-ray crystal structures of

use of an excess of TCNE in that case. In case of “pre- (Z)-16, (Z)-17, and (E)-17 (see Section S5 in the Supporting

dyad” 50, the CA-RE reaction proceeded with lower yields Information).

(70%), than in the case of 51 or (Ϯ)-54 (Ͼ 90%), pointing

Attempted double CA-RE reaction of porphyrin (Ϯ)-55

to an increased steric bulk imparted by the bicyclo[2.2.2]- with TCNE^[7b]resulted in a mixture of products, which

octane moiety. This is probably the reason why the CA-RE could not be characterized. Given that the same was true in

reaction with additional tri- (TCV) or dicyanovinyl (DCV) the case of reference (Ϯ)-66 (Section S1 in the Supporting

compounds was not successful for 50, except for the reac- Information), we realized that the decahydroquinoline moi-

tion with dicyanovinyl 56 under forcing conditions [N,N- ety was not a suitable choice as linker. The steric encum-

dimethylformamide (DMF), 120–130 °C, 6 d], which, how- brance of the decahydroquinoline moiety leads to a re-

ever, resulted in the unexpected formation of ZnP-S¹- duction of the electron-donating ability of its nitrogen lone-

DCBD 5, featuring a dicyanobuta-1,3-diene as acceptor. pair by forcing the N-aryl ring out of conjugation, as ob-

Given that reagent 56 was highly pure, as confirmed by ele- served in the X-ray crystal structure of (Ϯ)-55 (Figure 2),

1

mental analysis, we can only explain this unexpected loss of and in the H and ¹³C NMR spectra of the reference alk-

the F₃C-phenyl group through a reaction of 56 with DMF ynes (Ϯ)-65 and (Ϯ)-66. This reduced electron-pushing fea-

(or its formed Me₂NH impurity) under the harsh reaction ture affects the CA-RE reaction, possibly leading to com-

conditions to possibly yield 1,1-dicyanoethylene (see Sec- peting side reactions, and any formed tetracyanobuta-1,3-

tion S3 in the Supporting Information for more details). dienes become too reactive to be isolated by standard silica

The low yield of this transformation (21%) is in line with gel chromatography.^[36]

similar low yields obtained for the CA-RE reaction between

“pre-dyad” 51 and multicyanovinyl reagents 57–59 to afford

ZnP-S¹-TCBDderiv 6–8 in yields of 60, 26, and 25%,

respectively. The obtained yields are in accordance with the

relative reactivity of the DCV and TCV reagents, with 57

X-ray Crystal Structure of ZnP-S¹-DCBD 5·7EtOH

Single crystals of ZnP-S¹-DCBD 5·7EtOH suitable for

being the most electron-deficient olefin, and therefore the X-ray analysis were obtained by very slow evaporation of a

most reactive. The same trend was observed during the syn- CH₂Cl₂solution layered with EtOH on top at 23 °C in the

thesis of the reference compounds, which is reported in dark. The compound crystallized in the triclinic space

¯

Scheme S3 in the Supporting Information. Again, the lower group P1, with one EtOH molecule coordinated to the zinc

yields might be due to the steric hindrance resulting from ion and six additional disordered EtOH molecules in the

the bicyclo[2.2.2]octane moiety, because we have previously asymmetric unit (Figure 3, a and b). Such a highly solvated,

demonstrated that the CA-RE reaction with DCV and TCV sponge-like solid-state packing is characteristic for por-

derivatives can proceed in yields of 58–99%.^[35]

phyrins.^[37]Crystallization attempts with MeOH instead of

EtOH, or with any of the other conjugates with larger elec-

tron acceptors were unsuccessful.

The structure exhibits the same characteristics as ob-

served in the crystal structures of its individual components

(see Section S5 in the Supporting Information for ad-

ditional X-ray data): the dicyanobutadiene acceptor is dis-

torted around the central single bond with a torsional angle

of –79.2(4)°. The torsion angle between the DMA group

and its directly attached dicyanovinyl group is –32.7(5)°.

The push–pull interaction can be quantified by the quinoid

character δr of the DMA ring, which amounts to 0.037 Å

(for its definition and bond lengths, see the caption to Fig-

ure 3).^[38]The structure of the zinc porphyrin moiety is

comparable to the X-ray crystal structure of porphyrin

20·MeOH (Scheme 2), with absolute values for the torsion

angles about the bonds connecting the core to the meso-

aryl groups of 50–73°, and the zinc ion adopting a square-

pyramidal geometry by coordination of an EtOH molecule

[d(Zn···O) = 2.114 Å].

Scheme 4. Synthesis of the target electron donor–acceptor conju-

gates by the CA-RE reaction.

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Figure 3. X-ray crystal structure of ZnP–S¹–DCBD 5·7EtOH at 100 K with atomic displacement parameters drawn at 50% probability

level. H-atoms and EtOH solvent molecules are omitted for clarity. Color code: gray C, blue N, red O, steel blue Zn. (a) View onto the

porphyrin plane (omitting the EtOH ligand) showing the edge-to-edge electron donor–acceptor distance [Å] and the torsion angles θ [°]

of the aryl substituents; (b) side view (omitting tBu groups). Packing arrangement from two perpendicular views: (c) showing pairwise

edge-to-edge head-to-tail arrangement (EtOH molecules omitted); (d) showing stacking of alternating pairs of dyads with the distances

[Å] between the porphyrin planes indicated. The quinoid character is defined as: δr = [(a + aЈ)/2 + (c + cЈ)/2 – (b + bЈ)]/2.

Valuable information was also acquired on the geometry couple and are uncorrected from ohmic drop. The redox

of the linker moiety in ZnP-S¹-DCBD 5. The linker defines characteristics of the conjugates are summarized in Table 1;

the separation and electronic coupling between the electron those of the references are reported in Table S12 in the Sup-

donor and electron acceptor, which are decisive parameters porting Information.

in accounting for electron transfer phenomena. The PEP-

The electrochemical data of the electron donor–acceptor

bicyclo[2.2.2]octane linker S¹displays a rigid, rod-like struc- conjugates support the conclusion that the redox behavior

ture, still having some flexibility, as shown by its slightly of the porphyrin moieties is not impacted within the conju-

curved shape with an angle C(52)–C(51)–C(70) of 8.2(0)°. gates, with values similar to those of the ZnP-S 10 reference.

This curvature, probably evoked by crystal packing effects, As a matter of fact, the porphyrin undergoes two reversible

reduces, however, the edge-to-edge electron donor–acceptor one-electron oxidations at approximately +0.35 and

distance only minimally, which amounts to 16.856 Å +0.65 V, respectively, and two reversible one-electron re-

{d[C(51)···C(70)]}.

ductions at approximately –1.8 and –2.2 V.

The ZnP-S¹-DCBD 5 molecules arrange in a pairwise

head-to-tail fashion, whereby the intimate contacts between

the 3,5-di-tert-butyl groups and the linker lead to a slight

bending of the latter. The extension of this closely packaged

arrangement into a second dimension is brought about by

the pairwise interaction of the DMA groups on the electron

acceptors, which adopt an antiparallel alignment (Figure 3,

c). In a third packing dimension, shorter contacts are found

between alternating pairs of conjugates comprising π-π

stacking interactions between the linkers, and CH-π interac-

tions between the bicyclo[2.2.2]octyl moiety and the por-

phyrin π-system. The space between the pairs is solely filled

by EtOH solvent molecules, and no short contacts between

the conjugates are present (Figure 3, d).

A similar trend is observed for the push–pull butadiene

moieties within the conjugates, the potentials of which are

similar to those of the corresponding references. Such be-

havior is expected because no direct conjugation between

the porphyrin and the substituents exists. Therefore, the re-

sulting behavior is the sum of the behavior of the compo-

nents. Considering that the same trend was observed in our

previous multicomponent systems,^[11]we conclude that the

structural rigidification of the linker and modulation of the

acceptor moieties in this work did not alter the independent

redox behavior of the individual components.

The push–pull electron acceptors undergo a reversible

one-electron oxidation taking place at the DMA compo-

nent. For ZnP-S²-TCBD (Ϯ)-9, two reversible one-electron

oxidations are seen corresponding to the two anilino com-

ponents. The first reduction potentials of the electron ac-

ceptors span a range of 1.2 V from –1.78 V (ZnP-S¹-DCBD

Electrochemical Characterization

The redox properties of the electron donor–acceptor con- 5, comprising a dicyanobutadiene as the weakest acceptor)

jugates and their corresponding references were studied by to –0.58 V (ZnP-S¹-exTCNQ 2, comprising a TCNQ ad-

using cyclic voltammetry (CV) and rotating disk voltamme- duct as the strongest acceptor). The reduction strength is

try (RDV) in CH₂Cl₂containing nBu₄NPF₆(0.1 m). All po- in sound agreement with the number and type of electron-

tentials are given vs. the ferrocenium/ferrocene (Fc⁺/Fc) withdrawing groups. Only for ZnP-S¹-TCBD 3, with a tet-

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Photoactive, Rigid Porphyrin Conjugates

Table 1. Electrochemical data of electron donor–acceptor conjugates observed by cyclic voltammetry (CV) at a scan rate of ν = 0.1 Vs^–1

and rotating disk voltammetry (RDV) in CH₂Cl₂+ 0.1 m nBu₄NPF₆. All potentials are given vs. ferrocene, used as internal standard.

For the structural formulas of the compounds, see Figure 1.

Conjugate

Cyclic voltammetry

E° [V]^[a]

Rotating disk voltammetry

ΔE_p[mV]^[b]

E_p[V]^[c]

E_1/2[V]

Slope [mV]^[d]

ZnP-S¹-exTCNQ 1

+0.63

70

no well-defined

signal

+0.45

+0.35

–0.89

–1.83

–2.18

60

ZnP-S¹-exTCNQ 2

ZnP-S¹-TCBD 3

ZnP-S¹-TCBD 4

+0.65

90

+0.68^[e]

+0.45

+0.44 (1 e^–)

+0.35 (1 e^–)

–0.61 (1 e^–)

–0.79 (1 e^–)

–1.95^[e]

60

+0.35

–0.58

–0.75

–1.79

–2.08

60

90

85

+0.90

+0.64

+0.35

–1.21

–1.32

–1.84

–2.20

70

80

90

70

80

90

+0.92 (1 e^–)

+0.65 (1 e^–)

+0.36 (1 e^–)

–1.21 (1 e^–)

–1.38 (1 e^–)

–1.93 (1 e^–)

–2.28 (1 e^–)

70

120

140

100

+0.90

+0.64

+0.36

–0.79

–1.15

–1.82

–2.20

80

90

70

100

+0.90 (1 e^–)

+0.67 (1 e^–)

+0.36 (1 e^–)

–0.79 (1 e^–)

–1.19 (1 e^–)

60

100

–1.91 (1 e^–)

[e]

ZnP-S¹-DCBD 5

+0.73

+0.66

+0.35

–1.78

–1.88

–2.18

60

70

60

70

80

+0.69 (2 e^–)^[f]

+0.37 (1 e^–)

–1.83 (1 e^–)

–1.93 (1 e^–)

60

ZnP-S¹-TCBDderiv (E/Z)-6

+0.85

+0.62

+0.32

–1.06

–1.40

–1.83

–2.20

70

150

75

90

80

+0.87 (2 e^–)

+0.37 (1 e^–)

–1.10 (1 e^–)

–1.40 (1 e^–)

–2.10

110

100

140

210

–

ZnP-S¹-TCBDderiv (E/Z)-7

+0.83

+0.65

+0.35

–1.16

–1.38

–1.88

60

+0.86 (1 e^–)

+0.76 (1 e^–)

+0.41 (1 e^–)

–1.22 (1 e^–)

–1.44 (1 e^–)

–2.00 (1 e^–)

70

100

130

100

130

100

120

100

–2.24

ZnP-S¹-TCBDderiv (E/Z)-8

ZnP-S¹-TCBD (Ϯ)-9

+0.75

+0.65

+0.36

80

90

70

+0.75 (1 e^–)

+0.65 (1 e^–)

+0.36 (1 e^–)

–1.38 (1 e^–)

–1.82 (1 e^–)

–2.10

+0.93 (1 e^–)

+0.83 (1 e^–)

+0.75 (1 e^–)

+0.36 (1 e^–)

–1.06 (1 e^–)

–1.22 (1 e^–)

150

60

70

80

110

–1.40

–2.20

–1.82

70

+0.92

+0.81

+0.65

+0.35

–1.03

–1.23

–1.85

60

100

80

130

60

70

100

140

120

[a] E° = (E_pc+ E_pa)/2, where E_pcand E_pacorrespond to the cathodic and anodic peak potentials, respectively. [b] ΔE_p= E_pa– E_pc. [c] E_P

=

irreversible peak potential. [d] Logarithmic analysis of the wave obtained by plotting E vs. log [I/(I_lim– I)]; I_limis the limiting current and I the

current. [e] Small amplitude waves. [f] In contrast to CV, the second and third oxidations gave an unresolved two-electron wave.

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99

D. M. Guldi, F. Diederich et al.

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racyanobutadiene acceptor, did the first reduction potential When the applied potential was reset to zero, the oxidation

give rise to a substantial cathodic shift relative to ZnP-S¹- signatures decreased and the original spectrum was re-

TCBD 4 by 420 mV from –0.79 to –1.21 V. This cathodic stored. In the case of ZnP-S¹-TCBD 4, the same features

shift originates from the extra electron-accepting ethynediyl after the first one-electron oxidation arise upon applying

connected to the TCBD core in 4. Such an additional the same potential. Again, the latter indicates that no elec-

acetylene moiety has been shown in the past to account for tronic communication exists between the individual compo-

cathodic shifts up to approximately 200 mV.^[34]The ad- nents. During the first one-electron reduction of ZnP-S¹-

ditional cathodic shift up to 420 mV originates from the TCBD 4 (Figure 4, b), the feature at 468 nm, characteristic

bulk of the bicyclo[2.2.2]octyl group which enforces a for the intramolecular CT band, decreased and vanished. In

strong twist of the tetracyanobutadiene, leading to deconju- parallel, a new absorption evolves between 300 and 400 nm,

gation of the push–pull chromophore in ZnP-S¹-TCBD which maximizes at 368 nm. These features stem from the

3.^[34]The same effect is observed for ZnP-S¹-exTCNQ 1 and reduction of the TCBD moiety.

ZnP-S¹-exTCNQ 2, which exhibit a difference of 310 mV in

terms of their first reduction potentials.

Spectroelectrochemical investigations, in CH₂Cl₂con-

taining nBu₄NPF₆(0.1 m), confirmed the aforementioned

Quantum Chemical Calculations

observations. To illustrate the changes in the absorption

To obtain qualitative insights into the electronic struc-

spectra upon oxidation and reduction of ZnP-S 10 and tures of the electron donor–acceptor conjugates, DFT cal-

ZnP-S¹-TCBD 4, respectively, the differences in the optical culations at the B3LYP/6-31G(d) + LANL2DZ (on zinc)

density, ΔOD, were plotted against the wavelength (Fig- level of theory were undertaken using the Gaussian 09 soft-

ure 4). For ZnP-S 10, upon the first one-electron oxidation, ware package.^[40]As representative examples, the structures

evolutions of new absorptions were noted with well-re- of ZnP-S¹-TCBD 4 and the conformer of ZnP-S²-TCBD

solved isosbestic points at 413 and 434 nm (Figure 4, a). (Ϯ)-9 with the phenyl ring on the decahydroquinoline N-

Importantly, a newly developing absorption at 620 nm is atom departing equatorially, were fully optimized for a

discernible, which is a well-known characteristic for the zinc ground-state configuration in the gas phase and confirmed

porphyrin cation.^[39]In addition, features at 368, 448, and as minima according to the analysis of their analytical fre-

846 nm emerge as spectroscopic markers for the oxidation. quencies computed at the same level, which showed no

imaginary frequencies. To simplify calculations, the tert-

butyl groups were replaced by methyl groups.

The calculated structures are in good agreement with the

available experimental data from X-ray analysis for the por-

phyrin and push–pull acceptor moieties. The linkers of both

calculated structures are nearly completely linear. In the

conformer of ZnP-S²-TCBD (Ϯ)-9 with the equatorial N-

phenyl ring, the latter is substantially shifted out of the de-

cahydroquinoline plane by 53.5° due to steric interactions.

Computational studies on the second conformer of ZnP-

S²-TCBD (Ϯ)-9, with the N-phenyl ring adopting an axial

position, are included in Section S8 in the Supporting In-

formation.

The frontier molecular orbitals (FMOs) of ZnP-S¹-

TCBD 4 and ZnP-S²-TCBD (Ϯ)-9 are depicted in Figure 5.

The electron densities of the HOMO and LUMO are clearly

separated and located on the porphyrin and acceptor moie-

ties, respectively. This result backs up the electrochemical

data, which show a first and second oxidation taking place

on the porphyrins and a first reduction on the electron ac-

ceptors. Whereas the HOMO delocalizes to a minor extent

into the conjugated PEP-linker, the LUMO is clearly con-

fined by the saturated linker. Such an electronic distribution

is in line with our design considerations, whereby the elec-

tron acceptors exhibit diminished electronic couplings,

which might lead to longer lifetimes for the charge-sepa-

rated states.

Whereas the orbitals, located on the conjugated PEP

bridges (HOMO–2 and LUMO+4), are energetically well-

separated from the FMOs (HOMO and LUMO) that are

involved in the charge-transfer, the orbitals located on the

Figure 4. Differential absorption spectra following the electrochem-

ical oxidation of (a) ZnP-S 10 and the electrochemical reduction of

(b) ZnP-S¹-TCBD 4 in CH₂Cl₂+ 0.1 m nBu₄NPF₆.

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Photoactive, Rigid Porphyrin Conjugates

ene at 426 nm followed by Q-band absorption maxima at

551 and 591 nm (Figure 6). Linkage to S¹or S²slightly af-

fects the relative intensities and positions of the Q-bands in

the form of a minor redshift when contrasted to parent

meso-tetraphenylzinc porphyrin (ZnTPP). Further insight

into the characteristics of ZnP-S 10 stems from fluorescence

measurements. For ZnP-S 10, intense fluorescence maxima

evolve at 600 and 649 nm at room temperature with fluores-

cence quantum yields of 0.06 (inset, Figure 6).

The positions of the Soret- and Q-bands remain un-

changed in ZnP-S¹-exTCNQ 1 and ZnP-S¹-TCBD 3 when

compared to the reference ZnP-S 10. For ZnP-S¹-exTCNQ

1 and ZnP-S¹-TCBD 3, additional features are observable

at 458 and 588 nm, respectively. Both originate from a

charge-transfer (CT) involving the terminal strong electron

acceptors. These CT bands can be seen in all references 11 –

(Ϯ)-19 and arise from the push–pull interactions between

the multicyanobuta-1,3-diene acceptors and the directly

connected aniline rings. The CT character of this long-

wavelength absorption was corroborated by reversible pro-

tonation/deprotonation experiments, such as by using TFA/

K₂CO₃. Table S13 in the Supporting Information summa-

rizes the absorption characteristics of the CT bands for the

reference push–pull chromophores. The respective spectra

of the references are also gathered in Section S7.2 of the

Supporting Information. In line with previous results,

stronger electron-accepting character of the multi-

cyanobuta-1,3-dienes leads to more redshifted CT bands,

such as λ_max= 588 nm in 11 and 648 nm in 12. None of the

systems 11 – (Ϯ)-19 give rise to any appreciable fluores-

cence in the visible range at room temperature.

Table 2 summarizes the absorption bands for porphyrin

conjugates 1 – (Ϯ)-9. Overall, the absorption spectra of the

conjugates are best described as simple superimpositions of

the component spectra that lack notable perturbations or

additional CT transitions. This experimental evidence con-

firms that both the S¹and S²linkers disrupt the electronic

communication between the photo- and redox-active com-

ponents. Spectra for all porphyrin conjugates are collected

in Section S7.1 of the Supporting Information.

Figure 5. Frontier molecular orbitals of ZnP-S¹-TCBD 4 (left) and

ZnP-S²-TCBD (Ϯ)-9 with equatorial N-phenyl ring (right) shown

at 0.02 a.u., calculated at the B3LYP/6-31G(d) + LANL2DZ (on

zinc) level of theory.

saturated bridge are even farther apart in energy. This ener-

getic ordering, at least for a ground-state calculation, con-

solidates well the roles of the linker, namely, on one hand,

to spatially separate the HOMO from the LUMO and, on

the other hand, to limit the degree of electronic communi-

cation between porphyrin donor and push–pull acceptor.

Preliminary Steady-State Fluorescence Spectroscopy

To gain first insights on the electronic interactions be-

tween the photo- and redox-active components, the ground-

state absorption and fluorescence spectra of the electron

donor–acceptor conjugates were compared in toluene with

those of the individual components. For example, the ab-

sorption spectra of ZnP-S¹-exTCNQ 1, ZnP-S¹-TCBD 3,

and ZnP-S 10 are displayed in Figure 6. Reference por-

phyrin ZnP-S 10 displays an absorption spectrum that is

comparable to that of meso-tetraarylated zinc porphyrins.

In particular, the Soret-band absorption maximizes in tolu-

Insight into possible electron donor–acceptor interac-

tions between the different constituents came from fluores-

cence assays. In particular, we note porphyrin-centered

fluorescence bands at 600 and 649 nm for 1 – (Ϯ)-9 in tolu-

ene (Figure 6). Comparing the fluorescence quantum yields,

the weakest quenching is determined for ZnP-S¹-DCBD 5

(Φ_fl= 0.055) and ZnP-S¹-DCBDderiv (E/Z)-8 (Φ_fl= 0.055)

endowed with DCBD and its arylated derivative as electron

acceptors. In line with the reduction strength of the dif-

ferent electron acceptors, the fluorescence quenching inten-

sifies from ZnP-S¹-TCBD 3 (Φ_fl= 0.05), to ZnP-S¹-

TCBDderiv (E/Z)-7 (Φ_fl= 0.05), to ZnP-S¹-TCBD (E/Z)-6

(Φ_fl= 0.04), to ZnP-S²-TCBD (Ϯ)-9 (Φ_fl= 0.015), and to

ZnP-S¹-TCBD 4 (Φ_fl= 0.012). The strongest quenching of

the fluorescence is, however, seen for ZnP-S¹-exTCNQ 1

(Φ_fl= 0.003) and ZnP-S¹-exTCNQ 2 (Φ_fl= 0.005). ZnP-

S¹-exTCNQ 1 and ZnP-S¹-exTCNQ 2 feature an extended

TCNQ chromophore, which reveals the highest affinity

Figure 6. Absorption spectra of ZnP-S¹-exTCNQ 1 (solid line),

ZnP-S¹-TCBD 3 (dashed line), and ZnP-S 10 (dotted line) in tolu-

ene. Inset: fluorescence spectra after excitation at 426 nm in tolu-

ene.

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101

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Table 2. UV/Vis absorption spectroscopic data for porphyrin conjugates 1 – (Ϯ)-9 in toluene.

Conjugate

Soret-band [nm]

Q-bands [nm]

CT band of the push–pull butadiene chromophore [nm]

ZnP-S¹-exTCNQ 1

426

551/591

588

648

458

461

419

459

457

444

470

ZnP-S¹-exTCNQ 2

ZnP-S¹-TCBD 3

ZnP-S¹-TCBD 4

ZnP-S¹-DCBD 5

ZnP-S¹-TCBDderiv (E/Z)-6

ZnP-S¹-TCBDderiv (E/Z)-7

ZnP-S¹-TCBDderiv (E/Z)-8

ZnP-S¹-TCBD (Ϯ)-9

among the studied systems in terms of energy or electron gations, and theoretically corroborated by DFT electronic

transfer. According to the measured quantum yields, we as- structure calculations. Fluorescence quenching, which is in

sume that energy- or electron-transfer is possible in all elec- line with the acceptor strength, indicates that a rational

tron donor–acceptor conjugates. Further measurements, in- tuning of the photophysical properties by the push–pull

cluding time-resolved investigations, are necessary to shed chromophores as electron acceptors is possible.

light on the interactions between the different components.

Notably, the X-ray crystal structure data show that the

conjugates are geometrically well-defined systems, with the

electron-donor and electron-acceptor moieties held at fixed

edge-to-edge distances of approximately 17 Å for S¹, and

approximately 18 Å for S². Therefore, we can conclude that

any intramolecular intercomponent interactions, such as

electron transfer, if present, must result from through-bond

effects. In this regard, the trans-decahydroquinoline moiety

might provide an optimal geometry for stereoelectronic in-

teractions through its locked all-trans single bond skeleton,

because the extent of fluorescence quenching of ZnP-S²-

TCBD (Ϯ)-9 is comparable to that of ZnP-S¹-TCBD 4 de-

spite a difference in the first reduction potentials of 240 mV

(Förster resonance energy transfer is unlikely due to a lack

of spectral overlap between the porphyrin and acceptor

moieties).

A full account of the photophysical properties and analy-

sis according to the Marcus theory will be reported in a

subsequent article together with data for next-generation

electron donor–acceptor conjugates, comprising a new type

of rigid, short linker, enabling the incorporation of the

strongest push–pull chromophores with E°_red,1of possibly

up to +0.16 V.

Conclusions

We prepared a series of nine rigid, homologous zinc(II)

porphyrin-containing electron donor–acceptor conjugates,

in which we rationally incorporated push–pull chromo-

phores as electron acceptors covering a broad range of re-

duction potentials from –1.78 to –0.58 V (vs. Fc⁺/Fc).

The retrosynthetic strategy relied on a modular ap-

proach, whereby the individual building blocks, namely the

zinc porphyrin, the different linkers featuring “insulating”

bicyclo[2.2.2]octane or trans-decahydroquinoline spacers,

and the acetylenic acceptor-precursors were synthesized

first, assembled as the “pre-dyads”, and finally transformed

into the functional electron donor–acceptor conjugates by

the CA-RE reaction. Suitable reaction conditions for the

two key synthetic transformations, the Sonogashira reaction

and the Buchwald–Hartwig amination (BHA), were iden-

tified. A Cu-free Sonogashira reaction for deactivated

bromides was developed, giving reliable yields of approxi-

mately 40%, based on the alkynylporphyrin. The second

key reaction, the BHA, was effective only in low yields

(Ͻ 15%) for coupling to the decahydroquinoline linker, be-

cause tedious purification was required to remove small

amounts of palladium inserted into the free-base porphyrin.

However, this is one of the first examples of a late-stage

functionalization of structurally elaborate amino-substi-

tuted porphyrins by a BHA reaction; other reported exam-

ples mostly use bromoporphyrins or simple core-substituted

aminoporphyrins for the amination.^[41]

Experimental Section

General Details and Synthetic Procedures: The experimental details

for the synthesis and characterization of the target conjugates 1 –

(Ϯ)-9 are described in this manuscript; for the synthesis and char-

acterization of the “pre-dyads” and reference compounds, see Sec-

tion S2 in the Supporting Information. The atom numbering used

to assign the NMR signals is reported in the Supporting Infor-

mation. The purity of all target conjugates was verified by the clean

NMR spectra (see the Supporting Information) and high-resolu-

tion MALDI MS.

To analyze the multicomponent character of the electron

donor–acceptor conjugates in terms of their individual

components, the necessary references were also synthesized

and characterized. The novel electron donor–acceptor con-

jugates, control compounds, and synthetic intermediates

were fully characterized including X-ray crystal structure

analysis of the building blocks, references, “pre-dyad”

(Ϯ)-55, and ZnP-S¹-DCBD 5. The optoelectronic proper-

ties were assessed by electrochemical, spectroelectrochem-

ZnP-S¹-exTCNQ (1):

A mixture of porphyrin 50 (35 mg,

0.03 mmol) and TCNQ (6 mg, 0.03 mmol) in toluene (13 mL) was

stirred at 80 °C for 24 h. Evaporation and purification by flash

chromatography (SiO₂; cyclohexane/CH₂Cl₂, 1:1Ǟ0:1) gave 1

(28 mg, 70%) as a dark-purple metallic solid. Further purification

was carried out by sublimation (200 °C, 0.3 mbar) to remove re-

ical, and steady-state fluorescence spectroscopic investi- maining traces of TCNQ. R_f= 0.51 (SiO₂; CH₂Cl₂); m.p.Ն 300 °C

102

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Photoactive, Rigid Porphyrin Conjugates

(decomp.). ¹H NMR (600 MHz, CDCl₃; assignment based on a

a HSQC and a HMBC spectrum): δ = 29.75 [s; C(13ЈЈЈ)], 31.39,

COSY and a HSQC spectrum): δ = 1.52, 1.53 (2s, 54 H; 6 CMe₃), 31.74 [2 t, 6 C; C(14ЈЈЈ,15ЈЈЈ,17ЈЈЈ,18ЈЈЈ,19ЈЈЈ,20ЈЈЈ)], 31.91 (q, 18 C;

1.92 [t, J = 7.6 Hz, 6 H; H₂C(8ЈЈЈЈ,12ЈЈЈЈ,13ЈЈЈЈ)], 2.04–2.10 [m, 6 6 CMe₃), 34.25 [s; C(16ЈЈЈ)], 35.20 (s, 6 C; 6 CMe₃), 40.39 (q, 2 C;

H; H₂C(9ЈЈЈЈ,11ЈЈЈЈ,14ЈЈЈЈ)], 3.19 (s, 6 H; NMe₂), 6.83 [d, J = 9.2 Hz, NMe₂), 72.42 [s; C(4ЈЈЈ)C(CN)₂], 80.81 [s; C(3ЈЈ)], 89.50 [s;

2 H; H-C(3ЈЈЈЈ,5ЈЈЈЈ)], 6.94 [dd, J = 9.5, 2.0 Hz, 1 H; H-C(3ЈЈ or C(28ЈЈЈ)], 90.29 [s; C(27ЈЈЈ)], 95.71 [s; C(2ЈЈ)C(CN)₂], 111.08, 112.71

5ЈЈ)], 7.23–7.31 [m, 6 H; H-C(2ЈЈ,6ЈЈ,2ЈЈЈЈ,6ЈЈЈЈ,16ЈЈЈЈ,20ЈЈЈЈ)], 7.46 (2s; 2 CϵN), 112.41 [d, 2 C; C(9ЈЈЈ,11ЈЈЈ)], 114.87, 114.91 (2s; 2

[dd, J = 9.6, 2.0 Hz, 1 H; H-C(3ЈЈ or 5ЈЈ)], 7.59 [d, J = 8.6 Hz, 2 CϵN), 119.91 [s; C(29ЈЈЈ)], 120.97 [d, 3 C; 2 C(4Ј), C(10Ј)], 121.19

H; H-C(17ЈЈЈЈ,19ЈЈЈЈ)], 7.79 [t, J = 1.8 Hz, 1 H; H-C(10Ј)], 7.80 [t, [s; C(24ЈЈЈ)], 122.59 [s; C(5)], 122.71 [2s; C(10,20)], 122.91 [s; C(15)],

J = 1.8 Hz, 2 H; 2 H-C(4Ј)], 7.89 [d, J = 8.4 Hz, 2 H; H- 123.77 [s; C(7ЈЈЈ)], 124.64, 125.45 [2d; C(3ЈЈЈ,5ЈЈЈ)], 125.54 [s;

C(24ЈЈЈЈ,28ЈЈЈЈ)], 8.08 [d, J = 1.8 Hz, 2 H; H-C(8Ј,12Ј)], 8.09 [d, J C(4ЈЈ)], 125.68 [d, 2 C; C(22ЈЈЈ,26ЈЈЈ)], 129.73, 129.93 [2d, 4 C;

= 1.8 Hz, 4 H; 2 H-C(2Ј,6Ј)], 8.22 [d, J = 8.4 Hz, 2 H; H- C(8Ј,12Ј,30ЈЈЈ,34ЈЈЈ)], 129.79 [d, 4 C; 2 C(2Ј,6Ј)], 131.42 [s; C(1ЈЈЈ)],

C(25ЈЈЈЈ,27ЈЈЈЈ)], 8.95 [d, J = 4.6 Hz, 2 H; H-C(3,7)], 9.009 [d, J =

4.6 Hz, 2 H; H-C(2,8)], 9.011 [s, 4 H; H-C(12,13,17,18)] ppm. ¹³C

NMR (150 MHz, CDCl₃; assignment based on a HSQC and a

HMBC spectrum): δ = 30.78 [t, 3 C; C(9ЈЈЈЈ,11ЈЈЈЈ,14ЈЈЈЈ)], 31.79 [t,

131.57 [d, 2 C; C(3,7)], 131.81 [d, 2 C; C(23ЈЈЈ,25ЈЈЈ)], 132.35,

132.46, 132.58 [3d, 6 C; C(2,8,12,13,17,18)], 134.48, 136.31 [2d;

C(2ЈЈЈ,6ЈЈЈ)], 134.50 [d, 2 C; C(31ЈЈЈ,33ЈЈЈ)], 134.99 [d, 2 C;

C(8ЈЈЈ,12ЈЈЈ)], 141.90 [s, 3 C; 2 C(1Ј), C(7Ј)], 143.27 [s; C(32ЈЈЈ)],

3 C; C(8ЈЈЈЈ,12ЈЈЈЈ,13ЈЈЈЈ)], 31.91 (q, 18 C; 6 CMe₃), 34.86 [s; 148.68 [s, 2 C; C(9Ј,11Ј)], 148.71 [s, 4 C; 2 C(3Ј,5Ј)], 148.94 [s;

C(10ЈЈЈЈ)], 35.20 (s, 6 C; 6 CMe₃), 40.35 (q, 2 C; NMe₂), 41.68 [s; C(21ЈЈЈ)], 149.32 [s; C(1ЈЈ)], 149.91 [s, 2 C; C(4,6)], 150.54, 150.58,

C(7ЈЈЈЈ)], 72.20 [s; C(1ЈЈ)C(CN)₂], 89.62 [s; C(22ЈЈЈЈ)], 90.14, 90.17 150.66 [3s, 6 C; C(1,9,11,14,16,19)], 153.24 [s; C(10ЈЈЈ)], 154.29 [s;

[2s; C(21ЈЈЈЈ,3ЈЈЈ)], 111.97, 112.30 (2s; 2 CϵN), 112.63 [d, 2 C; C(4ЈЈЈ)], 155.65 [s; C(2ЈЈ)] ppm. IR (ATR): ν = 3063 (w), 2951 (m),

˜

C(3ЈЈЈЈ,5ЈЈЈЈ)], 114.66, 114.70 (2s; 2 CϵN), 119.87 [s; C(23ЈЈЈЈ)], 2905 (w), 2865 (w), 2205 (m), 1583 (s), 1521 (w), 1476 (w), 1408

120.09 [s; C(1ЈЈЈЈ)], 120.97 [d, 3 C; 2 C(4Ј), C(10Ј)], 121.35 [s;

(m), 1392 (m), 1361 (s), 1349 (s), 1326 (m), 1289 (m), 1247 (m),

C(18ЈЈЈЈ)], 122.52, 122.93 [2s; C(5,15)], 122.71 [s, 2 C; C(10,20)],

1220 (w), 1185 (s), 1170 (s), 1126 (w), 1067 (w), 1000 (m), 946 (w),

125.27, 125.45 [2d; C(2ЈЈ,6ЈЈ)], 125.52 [d, 2 C; C(16ЈЈЈЈ,20ЈЈЈЈ)], 929 (w), 899 (w), 882 (w), 859 (w), 823 (m), 796 (s), 715 (m), 674

129.72, 129.91 [2d, 4 C; C(8Ј,12Ј,24ЈЈЈЈ,28ЈЈЈЈ)], 129.79 [d, 4 C; 2

C(2Ј,6Ј)], 129.88 [s; C(4”)], 131.55 [d, 2 C; C(3,7)], 131.85 [d, 2 C;

(w) cm^–1. UV/Vis (toluene): λ_max(ε, m^–1cm^–1) = 648 (23300), 591

(25100), 552 (37900), 426 nm (615900); fluorescence (CHCl₃): λ_exc

= 550 nm; λ_em= 595, 647 nm. HRMS (MALDI; DCTB): m/z (%)

= 1597.7807 (29), 1596.7782 (50), 1595.7774 (62), 1594.7788 (74),

C(17ЈЈЈЈ,19ЈЈЈЈ)],

132.36,

132.47,

132.58

[3d,

6

C;

C(2,8,12,13,17,18)], 133.89 [d, 2 C; C(2ЈЈЈЈ,6ЈЈЈЈ)], 134.13, 135.43

[2d; C(3ЈЈ,5ЈЈ)], 134.50 [d, 2 C; C(25ЈЈЈЈ,27ЈЈЈЈ)], 141.89 [s, 3 C; 2 1593.7799 (84), 1592.7808 (100), 1591.7777 (82) {[M]⁺, calcd. for

C(1Ј), C(7Ј)], 143.32 [s; C(26ЈЈЈЈ)], 148.33 [s; C(15ЈЈЈЈ)], 148.68 [s, 2

C; C(9Ј,11Ј)], 148.71 [s, 4 C; 2 C(3Ј,5Ј)], 149.89 [s, 2 C; C(4,6)],

150.53, 150.59, 150.67 [3s, 6 C; C(1,9,11,14,16,19)], 153.07 [s;

C(4ЈЈЈЈ)], 153.88, 154.67 [2s; C(1ЈЈ,1ЈЈЈ)], 188.07 [s; C(2ЈЈЈ)] ppm. IR

C₁₀₈H₁₀₅N₉⁶⁴Zn⁺: 1591.7779}.

ZnP-S¹-TCBD (3): A mixture of porphyrin 50 (30 mg, 0.02 mmol)

and TCNE (3 mg, 0.02 mmol) in CH₂Cl₂(8 mL) was stirred at

23 °C for 4 h. Evaporation and purification by flash chromatog-

raphy (SiO₂; cyclohexane/CH₂Cl₂, 8:2Ǟ3:7) afforded 3 (23 mg,

70%) as a red solid. R_f= 0.34 (SiO₂; cyclohexane/CH₂Cl₂, 3:7);

m.p.Ն 300 °C (decomp.). ¹H NMR (400 MHz, CDCl₃; assignment

based on a COSY and a HSQC spectrum): δ = 1.529, 1.534 (2s, 54

H; 6 CMe₃), 1.96 [t, J = 7.8 Hz, 6 H; H₂C(8ЈЈЈ,12ЈЈЈ, 13ЈЈЈ)], 2.12–

2.20 [m, 6 H; H₂C(9ЈЈЈ,11ЈЈЈ,14ЈЈЈ)], 3.20 (s, 6 H; NMe₂), 6.80 [d, J

= 9.4 Hz, 2 H; H-C(3ЈЈЈ,5ЈЈЈ)], 7.30 [d, J = 8.5 Hz, 2 H; H-

C(16ЈЈЈ,20ЈЈЈ)], 7.61 [d, J = 8.4 Hz, 2 H; H-C(17ЈЈЈ,19ЈЈЈ)], 7.66 [d,

J = 9.3 Hz, 2 H; H-C(2ЈЈЈ,6ЈЈЈ)], 7.796 [t, J = 1.8 Hz, 1 H; H-

C(10Ј)], 7.803 [t, J = 1.8 Hz, 2 H; 2 H-C(4Ј)], 7.91 [d, J = 8.2 Hz,

2 H; H-C(24ЈЈЈ,28ЈЈЈ)], 8.09 [d, J = 1.8 Hz, 2 H; H-C(8Ј,12Ј)], 8.10

[d, J = 1.8 Hz, 4 H; 2 H-C(2Ј,6Ј)], 8.23 [d, J = 8.1 Hz, 2 H; H-

C(25ЈЈЈ,27ЈЈЈ)], 8.96 [d, J = 4.7 Hz, 2 H; H-C(3,7)], 9.017 [s, 4 H;

H-C(12,13,17,18)], 9.017 [d, J = 4.7 Hz, 2 H; H-C(2,8)] ppm. ¹³C

NMR (100 MHz, CDCl₃; assignment based on a HSQC and a

HMBC spectrum): δ = 30.82 [t, 3 C; C(9ЈЈЈ,11ЈЈЈ,14ЈЈЈ)], 31.79 [t, 3

C; C(8ЈЈЈ,12ЈЈЈ,13ЈЈЈ)], 31.91 (q, 18 C; 6 CMe₃), 34.75 [s; C(10ЈЈЈ)],

(ATR): ν = 3052 (w), 2952 (m), 2905 (w), 2866 (w), 2206 (m), 1583

˜

(s), 1521 (w), 1477 (w), 1442 (w), 1420 (m), 1409 (m), 1392 (m),

1363 (s), 1343 (s), 1323 (m), 1289 (w), 1267 (w), 1247 (w), 1220 (w),

1184 (s), 1169 (s), 1126 (m), 1067 (w), 1000 (m), 945 (w), 930 (w),

900 (w), 881 (w), 858 (w), 823 (m), 797 (m), 733 (w), 715 (m), 675

(w), 667 (w) cm^–1. UV/Vis (toluene): λ_max(ε, m^–1cm^–1) = 591

(45200), 552 (54800), 426 (612600), 335 nm (34200); fluorescence

(CHCl₃): λ_exc= 550 nm; λ_em= 595, 648 nm. HRMS (MALDI-MS;

DCTB): m/z (%) = 1573.7814 (26), 1572.779 (51), 1571.7784 (64),

1570.7799 (73), 1569.781 (85), 1568.7819 (100), 1567.7784 (84)

{[M]⁺, calcd. for C₁₀₆H₁₀₅N₉⁶⁴Zn⁺: 1567.7779}.

ZnP-S¹-exTCNQ (2):

A mixture of porphyrin 51 (35 mg,

0.03 mmol) and TCNQ (6 mg, 0.03 mmol) in toluene (13 mL) was

stirred at 80 °C for 25 h. Evaporation and purification by flash

chromatography (SiO₂; cyclohexane/CH₂Cl₂, 4:6Ǟ0:1) gave 2

(37 mg, 92%) as a dark-purple metallic solid. Further purification

was carried out by sublimation (200 °C, 0.3 mbar) to remove re-

maining traces of TCNQ. R_f= 0.59 (SiO₂; CH₂Cl₂); m.p.Ն 300 °C 35.20 (s, 6 C; 6 CMe₃), 40.32 (q, 2 C; NMe₂), 41.56 [s; C(7ЈЈЈ)],

(decomp.). ¹H NMR (600 MHz, CDCl₃; assignment based on a

74.94 [s; C(1ЈЈ)], 89.61 [s; C(22ЈЈЈ)], 90.18 [s; C(21ЈЈЈ)], 90.98 [s;

COSY and a HSQC spectrum): δ = 1.529, 1.534 (2s, 54 H; 6 CMe₃), C(4ЈЈ)], 111.31, 111.44 (2s; 2 CϵN), 112.43 [d, 2 C; C(3ЈЈЈ,5ЈЈЈ)],

1.90–1.96 [m, 6 H; H₂C(14ЈЈЈ,18ЈЈЈ,19ЈЈЈ)], 1.96–2.01 [m, 6 H; 113.83, 114.38 (2s; 2 CϵN), 115.76 [s; C(1ЈЈЈ)], 119.89 [s; C(23ЈЈЈ)],

H₂C(15ЈЈЈ,17ЈЈЈ,20ЈЈЈ)], 3.18 (s, 6 H; NMe₂), 6.78 [d, J = 9.2 Hz, 2 120.97 [d, 3 C; 2 C(4Ј), C(10Ј)], 121.38 [s; C(18ЈЈЈ)], 122.55 [s; C(5)],

H; H-C(9ЈЈЈ,11ЈЈЈ)], 7.23–7.36 [m, 4 H; H-C(2ЈЈЈ,3ЈЈЈ,5ЈЈЈ,6ЈЈЈ)], 7.29 122.70 [s, 2 C; C(10,20)], 122.91 [s; C(15)], 125.54 [d, 2 C;

[d, J = 9.2 Hz, 2 H; H-C(8ЈЈЈ,12ЈЈЈ)], 7.35 [d, J = 8.6 Hz, 2 H; H- C(16ЈЈЈ,20ЈЈЈ)], 129.73, 129.93 [2d, 4 C; C(8Ј,12Ј,24ЈЈЈ,28ЈЈЈ)], 129.80

C(22ЈЈЈ,26ЈЈЈ)], 7.62 [d, J = 8.6 Hz, 2 H; H-C(23ЈЈЈ,25ЈЈЈ)], 7.79 [t,

[d, 4 C; 2 C(2Ј,6Ј)], 131.56 [d, 2 C; C(3,7)], 131.88 [d, 2 C;

J = 1.8 Hz, 1 H; H-C(10Ј)], 7.80 [t, J = 1.8 Hz, 2 H; 2 H-C(4Ј)], C(17ЈЈЈ,19ЈЈЈ)], 131.90 [d, 2 C; C(2ЈЈЈ,6ЈЈЈ)], 132.35, 132.46, 132.58

7.91 [d, J = 8.3 Hz, 2 H; H-C(30ЈЈЈ,34ЈЈЈ)], 8.09 [d, J = 1.8 Hz, 2 [3d, 6 C; C(2,8,12,13,17,18)], 134.51 [d, 2 C; C(25ЈЈЈ,27ЈЈЈ)], 141.91

H; H-C(8Ј,12Ј)], 8.10 [d, J = 1.8 Hz, 4 H; 2 H-C(2Ј,6Ј)], 8.23 [d, J [s, 3 C; 2 C(1Ј), C(7Ј)], 143.32 [s; C(26ЈЈЈ)], 148.28 [s; C(15ЈЈЈ)],

= 8.4 Hz, 2 H; H-C(31ЈЈЈ,33ЈЈЈ)], 8.96 [d, J = 4.6 Hz, 2 H; H- 148.69 [s, 2 C; C(9Ј,11Ј)], 148.71 [s, 4 C; 2 C(3Ј,5Ј)], 149.91 [s, 2 C;

C(3,7)], 9.018 [s, 4 H; H-C(12,13,17,18)], 9.019 [d, J = 4.6 Hz, 2 H; C(4,6)], 150.54, 150.58, 150.67 [3s, 6 C; C(1,9,11,14,16,19)], 154.51

H-C(2,8)] ppm. ¹³C NMR (150 MHz, CDCl₃; assignment based on

[s; C(4ЈЈЈ)], 165.99 [s; C(2ЈЈ)], 183.63 [s; C(3ЈЈ)] ppm. IR (ATR): ν

˜

Eur. J. Org. Chem. 2015, 91–108

www.eurjoc.org

103

D. M. Guldi, F. Diederich et al.

FULL PAPER

= 3064 (w), 2953 (m), 2905 (w), 2867 (w), 2218 (w), 2163 (w), 1603 forded pure 5 as a purple solid. R_f= 0.18 (SiO₂; cyclohexane/

1

(s), 1493 (s), 1478 (m), 1439 (m), 1379 (s), 1362 (m), 1334 (m), 1290 CH₂Cl₂, 1:1). H NMR (600 MHz, CDCl₃; assignment based on a

(m), 1247 (m), 1207 (s), 1172 (s), 1124 (w), 1067 (w), 1001 (s), 946

(m), 930 (m), 899 (w), 883 (w), 859 (w), 822 (m), 798 (s), 732 (w),

715 (s), 651 (w) cm^–1. UV/Vis (toluene): λ_max(ε, m^–1cm^–1) = 590

(8500), 551 (31000), 458 (42000), 426 nm (677800); fluorescence

DQF-COSY and a HSQC spectrum): δ = 1.52, 1.53 (2s, 54 H; 6

CMe₃), 1.70–1.76 [m, 6 H; H₂C(8ЈЈЈ,12ЈЈЈ,13ЈЈЈ)], 1.81–1.87 [m, 6

H; H₂C(9ЈЈЈ,11ЈЈЈ,14ЈЈЈ)], 3.12 (s, 6 H; NMe₂), 5.31, 5.64 [2s, 2 H;

H₂C(4ЈЈ)], 6.71 [d, J = 9.3 Hz, 2 H; H-C(3ЈЈЈ,5ЈЈЈ)], 7.31 [d, J =

(CHCl₃): λ_exc= 550 nm; λ_em= 595, 647 nm. HRMS (MALDI, 8.7 Hz, 2 H; H-C(16ЈЈЈ,20ЈЈЈ)], 7.58 [d, J = 8.6 Hz, 2 H; H-

DCTB): m/z (%) = 1496.7463 (46), 1495.7455 (63), 1494.7464 (68), C(17ЈЈЈ,19ЈЈЈ)], 7.61 [d, J = 9.2 Hz, 2 H; H-C(2ЈЈЈ,6ЈЈЈ)], 7.785 [t, J

1493.7474 (81), 1492.7488 (100), 1491.7453 (89) {[M]⁺, calcd. for = 1.9 Hz, 1 H; H-C(10Ј)], 7.793 [t, J = 1.8 Hz, 2 H; 2 H-C(4Ј)],

C

₁₀₀H₁₀₁N₉⁶⁴Zn⁺: 1491.7466}.

7.90 [d, J = 8.4 Hz, 2 H; H-C(24ЈЈЈ,28ЈЈЈ)], 8.08 [d, J = 1.9 Hz, 2

H; H-C(8Ј,12Ј)], 8.09 [d, J = 1.8 Hz, 4 H; 2 H-C(2Ј,6Ј)], 8.21 [d, J

= 8.4 Hz, 2 H; H-C(25ЈЈЈ,27ЈЈЈ)], 8.95 [d, J = 4.6 Hz, 2 H; H-

C(3,7)], 9.00 [d, J = 4.6 Hz, 2 H; H-C(2,8)], 9.01 [s, 4 H; H-

C(12,13,17,18)] ppm. ¹³C NMR (150 MHz, CDCl₃; assignment

based on a HSQC and a HMBC spectrum): δ = 31.91 (q, 18 C; 6

ZnP-S¹-TCBD (4): A mixture of porphyrin 51 (30 mg, 0.02 mmol)

and TCNE (3 mg, 0.02 mmol) in CH₂Cl₂(8 mL) was stirred at

23 °C for 4 h. Evaporation and purification by flash chromatog-

raphy (SiO₂; cyclohexane/CH₂Cl₂, 1:1Ǟ2:8) gave 4 (31 mg, 95%)

as a purple solid. R_f= 0.33 (SiO₂; cyclohexane/CH₂Cl₂, 3:7); m.p.Ն

CMe₃), 32.00 [t,

3 C; C(8ЈЈЈ,12ЈЈЈ,13ЈЈЈ)], 32.39 [t, 3 C;

1

300 °C (decomp.). H NMR (400 MHz, CDCl₃; assignment based

C(9ЈЈЈ,11ЈЈЈ,14ЈЈЈ)], 34.77 [s; C(10ЈЈЈ)], 35.20 (s, 6 C; 6 CMe₃), 37.70

[s; C(7ЈЈЈ)], 40.17 (q, 2 C; NMe₂), 77.62 [s; C(1ЈЈ)], 89.27 [s;

C(22ЈЈЈ)], 90.44 [s; C(21ЈЈЈ)], 111.20 [d, 2 C; C(3ЈЈЈ,5ЈЈЈ)], 115.19,

115.55 (2s; 2 CϵN), 117.93 [t; C(4ЈЈ)], 119.94 [s; C(23ЈЈЈ)], 120.68,

120.80 [2s; C(1ЈЈЈ,18ЈЈЈ)], 120.96 [d, 3 C; 2 C(4Ј), C(10Ј)], 122.68 [s,

3 C; C(5,10,20)], 122.87 [s; C(15)], 125.71 [d, 2 C; C(16ЈЈЈ,20ЈЈЈ)],

129.73, 129.91 [2d, 4 C; C(8Ј,12Ј,24ЈЈЈ,28ЈЈЈ)], 129.80 [d, 4 C; 2

C(2Ј,4Ј)], 131.58 [d, 2 C; C(3,7)], 131.67 [d, 2 C; C(17ЈЈЈ,19ЈЈЈ)],

131.81 [d, 2 C; C(2ЈЈЈ,6ЈЈЈ)], 132.34, 132.44, 132.57 [3d, 6 C;

C(2,8,12,13,17,18)], 134.48 [d, 2 C; C(25ЈЈЈ,27ЈЈЈ)], 141.91 [s, 3 C; 2

C(1Ј), C(7Ј)], 143.19 [s; C(26ЈЈЈ)], 148.67 [s, 2 C; C(9Ј,11Ј)], 148.69

[s, 4 C; 2 C(3Ј,5Ј)], 149.92 [s, 3 C; C(4,6,15ЈЈЈ)], 150.53, 150.56,

150.65 [3s, 6 C; C(1,9,11,14,16,19)], 153.45 [s; C(4ЈЈЈ)], 153.96 [s;

on a COSY and a HSQC spectrum): δ = 1.53, 1.54 (2s, 54 H; 6

CMe₃), 1.92–2.01 [m, 6 H; H₂C(10ЈЈЈ,14ЈЈЈ,15ЈЈЈ)], 2.05–2.11 [m, 6

H; H₂C(11ЈЈЈ,13ЈЈЈ,16ЈЈЈ)], 3.20 (s, 6 H; NMe₂), 6.76 [d, J = 9.3 Hz,

2 H; H-C(3ЈЈЈ,5ЈЈЈ)], 7.36 [d, J = 8.5 Hz, 2 H; H-C(18ЈЈЈ,22ЈЈЈ)],

7.63 [d, J = 8.4 Hz, 2 H; H-C(19ЈЈЈ,21ЈЈЈ)], 7.73 [d, J = 9.3 Hz, 2

H; H-C(2ЈЈЈ,6ЈЈЈ)], 7.80 [t, J = 1.8 Hz, 1 H; H-C(10Ј)], 7.81 [t, J =

1.8 Hz, 2 H; 2 H-C(4Ј)], 7.92 [d, J = 8.1 Hz, 2 H; H-C(26ЈЈЈ,30ЈЈЈ)],

8.095 [d, J = 1.9 Hz, 2 H; H-C(8Ј,12Ј)], 8.104 [d, J = 1.8 Hz, 4 H;

2 H-C(2Ј,6Ј)], 8.24 [d, J = 8.2 Hz, 2 H; H-C(27ЈЈЈ,29ЈЈЈ)], 8.97 [d, J

= 4.7 Hz, 2 H; H-C(3,7)], 9.020 [s, 4 H; H-C(12,13,17,18)], 9.023

[d, J = 4.7 Hz, 2 H; H-C(2,8)] ppm. ¹³C NMR (100 MHz, CDCl₃;

assignment based on a HSQC spectrum): δ = 30.01 [s; C(9ЈЈЈ)],

31.38, 31.66 [2 t, 6 C; C(10ЈЈЈ,11ЈЈЈ,13ЈЈЈ,14ЈЈЈ,15ЈЈЈ,16ЈЈЈ)], 31.91 (q,

18 C; 6 CMe₃), 34.31 [s; C(12ЈЈЈ)], 35.20 (s, 6 C; 6 CMe₃), 40.34 (q,

2 C; NMe₂), 74.62 [s; C(1ЈЈ)], 78.25 [s; C(7ЈЈЈ)], 89.49 [s; C(24ЈЈЈ)],

90.32 [s; C(23ЈЈЈ)], 95.91 [s; C(4ЈЈ)], 110.20, 111.50 (2s; 2 CϵN),

112.20 [d, 2 C; C(3ЈЈЈ,5ЈЈЈ)], 113.24, 114.41 (2s; 2 CϵN), 117.85 [s;

C(1ЈЈЈ)], 119.93 [s; C(25ЈЈЈ)], 120.98 [d, 3 C; 2 C(4Ј), C(10Ј)], 121.19

[s; C(20ЈЈЈ)], 122.63 [s; C(5)], 122.72 [s, 2 C; C(10,20)], 122.91 [s;

C(15)], 125.70 [d, 2 C; C(18ЈЈЈ,22ЈЈЈ)], 128.08 [s; C(8ЈЈЈ)], 129.73,

129.94 [2d, 4 C; C(8Ј,12Ј,26ЈЈЈ,30ЈЈЈ)], 129.80 [d, 4 C; 2 C(2Ј,6Ј)],

131.59 [d, 2 C; C(3,7)], 131.81 [d, 2 C; C(19ЈЈЈ,21ЈЈЈ)], 132.36,

132.46, 132.59 [3d, 6 C; C(2,8,12,13,17,18)], 132.55 [d, 2 C;

C(2ЈЈЈ,6ЈЈЈ)], 134.51 [d, 2 C; C(27ЈЈЈ,29ЈЈЈ)], 141.91 [s, 2 C; 2 C(1Ј)],

141.92 [s; C(7Ј)], 143.27 [s; C(28ЈЈЈ)], 148.69 [s, 2 C; C(9Ј,11Ј)],

148.72 [s, 4 C; 2 C(3Ј,5Ј)], 148.96 [s; C(17ЈЈЈ)], 149.93 [s, 2 C;

C(4,6)], 150.55, 150.59, 150.67 [3s, 6 C; C(1,9,11,14,16,19)], 152.07

C(3ЈЈ)], 177.21 [s; C(2ЈЈ)] ppm. IR (ATR): ν = 3064 (w), 2957 (m),

˜

2906 (m), 2864 (m), 2224 (w), 2162 (w), 1804 (w), 1708 (w), 1600

(s), 1549 (w), 1514 (m), 1495 (m), 1477 (m), 1445 (m), 1425 (m),

1392 (w), 1362 (s), 1338 (m), 1288 (m), 1247 (m), 1220 (m), 1201

(m), 1185 (m), 1169 (m), 1067 (w), 999 (s), 947 (w), 930 (m), 899

(w), 881 (w), 859 (w), 820 (s), 796 (s), 764 (w), 732 (w), 716 (s) cm^–1.

UV/Vis (PhCN): λ_max(ε, m^–1cm^–1) = 605 (24400), 564 (35800),

432 nm (617900); fluorescence (CHCl₃): λ_exc= 550 nm; λ_em= 595,

646 nm. HRMS (MALDI, DCTB): m/z (%) = 1447.7591 (24),

1446.7562 (47), 1445.7549 (61), 1444.7565 (71), 1443.7571 (80),

1442.7591 (100), 1441.7556 (92) {[M]⁺, calcd. for C₉₈H₁₀₃N₇⁶⁴Zn⁺:

1441.7561}.

ZnP-S¹-TCBDderiv (E/Z)-6: A mixture of porphyrin 51 (50 mg,

0.04 mmol) and 57 (20 mg, 0.07 mmol) in 1,1,2,2-tetrachloroethane

(6 mL) was stirred at 120 °C for 61 h. Evaporation and flash

chromatography (SiO₂; cyclohexane/CH₂Cl₂, 6:4Ǟ35:70) gave 6

(36 mg, 60%; E/Z ratio 1:2) as a purple solid. R_f= 0.69, 0.38 (SiO₂;

cyclohexane/CH₂Cl₂, 2:8). ¹H NMR [400 MHz, CD₂Cl₂; assign-

ment based on a COSY and a HSQC spectrum; Z/E ratio 2:1]: δ

[s; C(3ЈЈ)], 154.59 [s; C(4ЈЈЈ)], 160.79 [s; C(2ЈЈ)] ppm. IR (ATR): ν

˜

= 3062 (w), 2958 (m), 2905 (w, sh), 2867 (m), 2222 (m), 2185 (m),

1813 (w), 1698 (w), 1607 (s), 1501 (s), 1441 (m), 1381 (s), 1361 (s),

1339 (s), 1310 (m), 1290 (m), 1275 (m), 1246 (m), 1213 (s), 1190

(m), 1173 (s), 1066 (w), 1001 (s), 946 (m), 929 (m), 899 (w), 887

(w), 861 (w), 822 (s), 800 (s), 750 (w), 734 (w), 716 (m), 666

(w) cm^–1. UV/Vis (toluene): λ_max(ε, m^–1cm^–1) = 591 (13100), 552

(35600), 461 (weak, 20200), 426 nm (658900); fluorescence

(CHCl₃): λ_exc= 550 nm; λ_em= 595, 646 nm. HRMS (MALDI,

DCTB): m/z (%) = 1521.7490 (25), 1520.7465 (46), 1519.7455 (59),

1518.7467 (68), 1517.7477 (80), 1516.7488 (100), 1515.7458 (88)

{[M]⁺, calcd. for C₁₀₂H₁₀₁N₉⁶⁴Zn⁺: 1515.7466}.

ZnP-S¹-DCBD (5): A mixture of porphyrin 50 (40 mg, 0.03 mmol)

and 56 (26 mg, 0.12 mmol) in DMF (6 mL) was stirred at 120–

130 °C for 6 d. Evaporation and two rounds of MPLC (SiO₂; cyclo-

hexane/CH₂Cl₂, 8:2Ǟ1:1) gave impure 5 (9 mg, 21%) as a purple

solid. An analytically pure sample was obtained by treating a solu-

tion of impure 5 in CH₂Cl₂(3 mL) with Zn(OAc)₂·2H₂O (20 mg,

0.09 mmol) in MeOH (1 mL), and stirring at 23 °C for 14 h. Evapo-

ration and preparative TLC (SiO₂; cyclohexane/CH₂Cl₂, 1:1) af-

=

1.55 (s, 54 H;

6

CMe₃), 1.79–1.94 [m, 8.1 H;

H₂C(16ЈЈЈ,17ЈЈЈ,19ЈЈЈ,20ЈЈЈ,21ЈЈЈ,22ЈЈЈ), (Z)-isomer], 1.98 [dd, J =

10.3, 5.5 Hz, 1.95 H; H₂C(16ЈЈЈ,20ЈЈЈ,21ЈЈЈ), (E)-isomer], 2.12 [dd,

J = 10.6, 5.2 Hz, 1.95 H; H₂-C(17ЈЈЈ,19ЈЈЈ,22ЈЈЈ), (E)-isomer], 3.10

[s, 1.95 H; NMe₂, (E)-isomer], 3.18 [s, 4.05 H; NMe₂, (Z)-isomer],

6.62 [d, J = 9.3 Hz, 0.65 H; H-C(3ЈЈЈ,5ЈЈЈ), (E)-isomer], 6.82 [d, J

= 9.3 Hz, 1.35 H; H-C(3ЈЈЈ,5ЈЈЈ), (Z)-isomer], 7.35 [d, J = 8.4 Hz,

1.35 H; H-C(24ЈЈЈ,28ЈЈЈ), (Z)-isomer], 7.41 [d, J = 8.3 Hz, 0.65 H;

H-C(24ЈЈЈ,28ЈЈЈ), (E)-isomer], 7.53 [d, J = 9.2 Hz, 0.65 H; H-

C(2ЈЈЈ,6ЈЈЈ), (E)-isomer], 7.61 [d,

J = 8.3 Hz, 1.35 H; H-

C(25ЈЈЈ,27ЈЈЈ), (Z)-isomer], 7.64 [d, J = 8.7 Hz, 0.65 H; H-

C(25ЈЈЈ,27ЈЈЈ), (E)-isomer], 7.86 [s, 3 H; 2 H-C(4Ј), H-C(10Ј)], 7.89

[d, J = 9.4 Hz, 1.35 H; H-C(2ЈЈЈ,6ЈЈЈ), (Z)-isomer], 7.93 [d, J =

7.9 Hz, 2 H; H-C(32ЈЈЈ,36ЈЈЈ)], 8.11 [s, 6 H; 2 H-C(2Ј,6Ј), H-

C(8Ј,12Ј)], 8.24 [d, J = 7.7 Hz, 2 H; H-C(33ЈЈЈ,35ЈЈЈ)], 8.98 [d, J =

104

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Eur. J. Org. Chem. 2015, 91–108

Photoactive, Rigid Porphyrin Conjugates

4.5 Hz, 2 H; H-C(3,7)], 9.01 [s, 4 H; H-C(12,13,17,18)], 9.01–9.04 [d, J = 8.4 Hz, 2 H; H-C(25ЈЈЈ,27ЈЈЈ), (Z/E)-isomers], 7.80 [d, J =

[m, 2 H; H-C(2,8)] ppm. ¹³C NMR [100 MHz, CD₂Cl₂; assignment 7.5 Hz, 2 H; H-C(9ЈЈЈ,11ЈЈЈ), (Z)-isomer; H-C(2ЈЈЈ,6ЈЈЈ), (E)-iso-

based on a HSQC spectrum and reference compounds, assignment

could not be fully confirmed; Z/E ratio 2:1]: δ = 29.55 [s; C(15ЈЈЈ)],

mer], 7.84–7.87 [m, 3 H; 2 H-C(4Ј), H-C(10Ј), (Z/E)-isomers], 7.88

[d, J = 9.3 Hz, 1.4 H; H-C(2ЈЈЈ,6ЈЈЈ), (Z)-isomer], 7.93 [d, J =

31.80, 32.25 [2 t, 6 C; C(16ЈЈЈ,17ЈЈЈ,19ЈЈЈ,20ЈЈЈ,21ЈЈЈ,22ЈЈЈ), ad- 8.2 Hz, 2 H; H-C(32ЈЈЈ,36ЈЈЈ), (Z/E)-isomers], 8.08–8.13 [m, 6 H; 2

ditional peaks of these carbons are probably hidden by the peak at H-C(2Ј,6Ј), H-C(8Ј,12Ј), (Z/E)-isomers], 8.16 [d, J = 8.0 Hz, 1.4 H;

32.04], 32.04 [q, 18 C; 6 CMe₃, (E)-isomer], 34.62 [s; C(18ЈЈЈ)], H-C(8ЈЈЈ,12ЈЈЈ), (Z)-isomer], 8.24 [d, 8.2 Hz, H; H-

J

=

2

35.52 (s, 6 C; 6 CMe₃), 40.48 [q, 2 C; NMe₂, (E)-isomer], 40.56 [q, C(33ЈЈЈ,35ЈЈЈ), (Z/E)-isomers], 8.978 [d, J = 4.7 Hz, 1.4 H; H-

2 C; NMe₂, (Z)-isomer], 74.93, 77.26, 78.83 [3s; C(1ЈЈ,13ЈЈЈ), Z/E- C(3,7), (Z)-isomer], 8.983 [d, J = 4.7 Hz, 0.6 H; H-C(3,7), (E)-

isomers], 89.68 [s; C(30ЈЈЈ)], 90.70 [s; C(29ЈЈЈ)], 109.36 [s; C(4ЈЈ or

7ЈЈЈ)], 111.88 [d, 2 C; C(3ЈЈЈ,5ЈЈЈ), (E)-isomer], 112.36 [d, 2 C;

isomer], 9.007 [s, 4 H; H-C(12,13,17,18), (Z/E)-isomers], 9.019 [d,

J = 4.8 Hz, 1.4 H; H-C(2,8), (Z)-isomer], 9.021 [d, J = 4.7 Hz,

C(3ЈЈЈ,5ЈЈЈ), (Z)-isomer], 113.90, 115.38, 115.62 [3s; 3 CϵN, (E)- 0.6 H; H-C(2,8), (E)-isomer] ppm. ¹³C NMR [100 MHz, CD₂Cl₂;

isomer], 114.22, 114.29, 115.49 [3s; 3 CϵN, (Z)-isomer], 118.55 [s;

C(1ЈЈЈ), (Z)-isomer], 118.63 [s; C(1ЈЈЈ), (E)-isomer], 120.35, 120.37

[2s; C(31ЈЈЈ) and C(14ЈЈЈ), (Z)- or (E)-isomer], 120.86 [s; C(26ЈЈЈ)],

assignment based on a HSQC spectrum and reference compounds,

assignment could not be fully confirmed; Z/E ratio 7:3]: δ = 29.77

[s; C(15ЈЈЈ)], 31.88, 32.39 [2 t, 6 C; C(16ЈЈЈ,17ЈЈЈ,19ЈЈЈ, 20ЈЈЈ,

121.64 [d, 3 C; 2 C(4Ј), C(10Ј)], 123.05 [s, 2 C; C(10,20)], 123.10, 21ЈЈЈ,22ЈЈЈ)], 32.04 (q, 18 C; 6 CMe₃), 34.67 [s; C(18ЈЈЈ)], 35.52 (s,

123.22 [2s; C(5,15)], 126.22 [d, 2 C; C(24ЈЈЈ,28ЈЈЈ), (Z)-isomer], 6 C; 6 CMe₃), 40.51 [q, 2 C; NMe₂, (E)-isomer], 40.54 [q, 2 C;

126.30 [d, 2 C; C(24ЈЈЈ,28ЈЈЈ), (E)-isomer], 130.15, 130.30 [2d;

NMe₂, (Z)-isomer], 74.93, 75.12, 78.05, 79.28 [4s; C(1ЈЈ,13ЈЈЈ), (Z/

C(8Ј,12Ј,32ЈЈЈ,36ЈЈЈ)], 130.21 [d, 4 C; 2 C(2Ј,6Ј)], 131.98 [d, 2 C; E)-isomers], 89.64, 89.68 [2s; C(30ЈЈЈ), (Z/E)-isomers], 90.72, 90.78

C(3,7)], 132.07 [d, 2 C; C(25ЈЈЈ,27ЈЈЈ)], 132.29 [d, 2 C; C(2ЈЈЈ,6ЈЈЈ), [2s; C(29ЈЈЈ), (Z/E)-isomers], 112.17 [d, 2 C; C(3ЈЈЈ,5ЈЈЈ), (E)-iso-

(E)-isomer], 132.69, 132.79, 132.92 [3d, 6 C; C(2,8,12,13,17,18)],

132.97 [d, C; C(2ЈЈЈ,6ЈЈЈ), (Z)-isomer], 135.05 [d, C;

C(33ЈЈЈ,35ЈЈЈ)], 142.33 [s, 3 C; 2 C(1Ј), C(7Ј)], 143.16 [s; C(3ЈЈ)],

mer], 112.21 [d, 2 C; C(3ЈЈЈ,5ЈЈЈ), (Z)-isomer], 114.63, 115.67,

116.33 [3s; 3 CϵN, (Z)-isomer], 115.06, 115.48, 118.60 [3s; 3 CϵN,

(E)-isomer], 117.48 [s; C(14ЈЈЈ), (E)-isomer], 118.96 [s; C(1ЈЈЈ), (E)-

2

143.65 [s; C(34ЈЈЈ)], 149.32 [s, 6 C; 2 C(3Ј,5Ј), C(9Ј,11Ј)], 149.94 [s; isomer], 119.00 [s; C(1ЈЈЈ), (Z)-isomer], 120.37 [s; C(31ЈЈЈ)], 120.38

C(23ЈЈЈ)], 150.34 [s, 2 C; C(4,6)], 150.96, 150.98, 151.08 [3s, 6 C;

C(1,9,11,14,16,19)], 154.55 [s; C(4ЈЈЈ), (Z)-isomer], 154.96 [s;

C(4ЈЈЈ), (E)-isomer], 163.63 [s; C(2ЈЈ), (Z)-isomer], 163.77 [s; C(2ЈЈ),

(E)-isomer] ppm, C[14ЈЈЈ, (Z)- or (E)-isomer] could not be assigned,

[s; C(14ЈЈЈ), (Z)-isomer], 121.24 [s; C(4ЈЈ), (E)-isomer], 121.31 [s;

C(4ЈЈ), (Z)-isomer], 121.65 [d, 3 C; 2 C(4Ј), C(10Ј)], 121.82 [s;

C(26ЈЈЈ)], 123.06 [s, 2 C; C(10,20)], 123.10, 123.23 [2s; C(5,15)],

126.15 [dq, ³J(C,F) = 3.8 Hz, 2 C; C(9ЈЈЈ,11ЈЈЈ), (Z)-isomer], 126.25

C(4ЈЈ or 7ЈЈЈ) and C(8ЈЈЈ,9ЈЈЈ,10ЈЈЈ,11ЈЈЈ,12ЈЈЈ) missing (hidden by [d, 2 C; C(24ЈЈЈ,28ЈЈЈ), (Z)-isomer], 126.29 [d, 2 C; C(24ЈЈЈ,28ЈЈЈ),

the noise). ¹⁹F NMR [377 MHz, CD₂Cl₂; Z/E ratio 2:1]: δ =

–161.00 [td, J = 21.4, 7.2 Hz, 1.35 F; F-C(9ЈЈЈ,11ЈЈЈ), (Z)-isomer],

(E)-isomer], 126.42 [dq, ³J(C,F) = 3.9 Hz, 2 C; C(9ЈЈЈ,11ЈЈЈ), (E)-

isomer], 129.20 [d, 2 C; C(8ЈЈЈ,12ЈЈЈ), (E)-isomer], 129.53 [d, 2 C;

–160.58 [td, J = 20.4, 5.2 Hz, 0.65 F; F-C(9ЈЈЈ,11ЈЈЈ), (E)-isomer], C(8ЈЈЈ,12ЈЈЈ),

(Z)-isomer],

130.15,

130.31 [2d,

4

C;

–150.12 [t, J = 21.0 Hz, 0.68 F; F-C(10ЈЈЈ), (Z)-isomer], –149.57 [t, C(8Ј,12Ј,32ЈЈЈ,36ЈЈЈ)], 130.21 [d, 4 C; 2 C(2Ј,6Ј)], 131.99 [d, 2 C;

J = 21.2 Hz, 0.35 F; F-C(10ЈЈЈ), (E)-isomer], –136.14 [dt, J = 20.9, C(3,7)], 132.08 [d, 2 C; C(25ЈЈЈ,27ЈЈЈ)], 132.20 [q, ²J(C,F) = 33.0 Hz;

5.8 Hz, 0.65 F; F-C(8ЈЈЈ,12ЈЈЈ), (E)-isomer], –135.53 [br. d, J = C(10ЈЈЈ), (E)-isomer], 132.59 [q, ²J(C,F) = 32.7 Hz; C(10ЈЈЈ), (Z)-

18.6 Hz, 1.35 F; F-C(8ЈЈЈ,12ЈЈЈ), (Z)-isomer] ppm. IR (ATR): ν =

isomer], 132.70, 132.79, 132.92 [3d, 6 C; C(2,8,12,13,17,18)], 132.97

[d, 2 C; C(2ЈЈЈ,6ЈЈЈ), (E)-isomer], 133.04 [d, 2 C; C(2ЈЈЈ,6ЈЈЈ), (Z)-

isomer], 135.06 [d, 2 C; C(33ЈЈЈ,35ЈЈЈ)], 135.10, 135.78, 136.07 [3s;

C(3ЈЈ,7ЈЈЈ), (Z/E)-isomers], 142.33 [s, 3 C; 2 C(1Ј), C(7Ј)], 143.65 [s;

C(34ЈЈЈ)], 149.31 [s, 2 C; C(9Ј,11Ј)], 149.33 [s, 4 C; 2 C(3Ј,5Ј)],

˜

2953 (m), 2927 (m), 2867 (m), 2219 (w), 2202 (w), 1702 (w), 1654

(w), 1604 (s), 1520 (m), 1496 (s), 1440 (m), 1379 (m), 1362 (m),

1340 (m), 1291 (w), 1248 (m), 1208 (m), 1190 (m), 1172 (m), 1116

(w), 1067 (w), 1001 (s), 986 (m), 947 (w), 929 (w), 900 (w), 884 (w),

860 (w), 822 (m), 798 (s), 746 (w), 733 (w), 717 (m), 628 (w) cm^–1. 150.06 [s; C(23ЈЈЈ)], 150.34 [s, 2 C; C(4,6)], 150.96, 150.99, 151.08

UV/Vis (toluene): λ_max(ε, m^–1cm^–1) = 591 (6800), 552 (23500), 459 [3s, 6 C; C(1,9,11,14,16,19)], 154.75 [s; C(4ЈЈЈ), (E)-isomer], 154.82

(24000), 426 nm (472800); fluorescence (CHCl₃): λ_exc= 550 nm; λ_em[s; C(4ЈЈЈ), (Z)-isomer], 164.04 [s; C(2ЈЈ), (E)-isomer], 166.07 [s;

= 596, 647 nm. HRMS (MALDI, DCTB): m/z (%) = 1663.7420

C(2ЈЈ), (Z)-isomer] ppm, C(q; CF₃) signal hidden by the noise. ¹⁹F

(11), 1662.7392 (28), 1661.7371 (51), 1660.7363 (67), 1659.7378 NMR [377 MHz, CD₂Cl₂; Z/E ratio 7:3]: δ = –63.37 [s; CF₃, (E)-

(75), 1658.7389 (90), 1657.7397 (100), 1656.7364 (83) {[M]⁺, calcd.

for C₁₀₇H₁₀₁F₅N₈⁶⁴Zn⁺: 1656.7355}.

isomer], –63.22 [s; CF , (Z)-isomer] ppm. IR (ATR): ν = 3064 (w),

˜

3

2952 (m), 2905 (w), 2866 (w), 2219 (w), 2193 (w), 1603 (s), 1594

(m), 1494 (m), 1479 (m), 1439 (w), 1377 (m), 1362 (m), 1339 (m),

1323 (s), 1290 (m), 1247 (m), 1207 (m), 1170 (s), 1131 (s), 1070 (m),

1016 (w), 1001 (s), 946 (w), 930 (m), 899 (w), 882 (w), 861 (w), 845

(m), 822 (s), 797 (s), 765 (w), 733 (m), 716 (s) cm^–1. UV/Vis (tolu-

ene): λ_max(ε, m^–1cm^–1) = 591 (9900), 552 (30700), 457 (38900),

426 nm (635700); fluorescence (CHCl₃): λ_exc= 550 nm; λ_em= 595,

647 nm. HRMS (MALDI, DCTB): m/z (%) = 1641.7757 (12),

1640.7732 (30), 1639.7708 (51), 1638.7695 (69), 1637.7711 (77),

1636.7723 (90), 1635.7727 (100), 1634.7692 (84) {[M]⁺, calcd. for

C₁₀₈H₁₀₅F₃N₈⁶⁴Zn⁺: 1634.7700}.

ZnP-S¹-TCBDderiv (E/Z)-7: A mixture of porphyrin 51 (36 mg,

0.03 mmol) and 58 (12 mg, 0.05 mmol) in 1,1,2,2-tetrachloroethane

(5 mL) was stirred at 120 °C for 62 h. Evaporation and flash

chromatography (SiO₂; cyclohexane/CH₂Cl₂, 6:4Ǟ3:7) gave 7

(11 mg, 26%; E/Z ratio 3:7) as a purple solid. R_f= 0.69, 0.42 (SiO₂;

cyclohexane/CH₂Cl₂, 2:8); m.p.Ն 300 °C (decomp.). ¹H NMR

[400 MHz, CD₂Cl₂; assignment based on

a COSY and a

HSQC spectrum; Z/E ratio 7:3]: δ = 1.55 [s, 54 H; 6 CMe₃, (Z/

E)-isomers], 1.91–1.99 [m, 10 H; H₂C(16ЈЈЈ,20ЈЈЈ,21ЈЈЈ), (E)-isomer;

H₂C(16ЈЈЈ,17ЈЈЈ,19ЈЈЈ,20ЈЈЈ,21ЈЈЈ,22ЈЈЈ), (Z)-isomer], 2.01–2.08 [m, 2

H; H₂C(17ЈЈЈ,19ЈЈЈ,22ЈЈЈ), (E)-isomer], 3.14 [s, 2 H; NMe₂, (E)-iso-

mer], 3.17 [s, 4 H; NMe₂, (Z)-isomer], 6.71 [d, J = 9.4 Hz, 0.6 H;

ZnP-S¹-DCBDderiv (E/Z)-8: A mixture of porphyrin 51 (50 mg,

0.04 mmol) and 59 (13 mg, 0.07 mmol) in 1,1,2,2-tetrachloroethane

(4.5 mL) was stirred at 120 °C for 61 h. Evaporation and flash

chromatography (SiO₂; cyclohexane/CH₂Cl₂, 6:4Ǟ0:1) gave 8

(14 mg, 25%; E/Z ratio 10:1) as a purple solid. An analytically pure

sample was obtained by removal of impurities by sublimation

H-C(3ЈЈЈ,5ЈЈЈ), (E)-isomer], 6.79 [d,

J = 9.4 Hz, 1.4 H; H-

C(3ЈЈЈ,5ЈЈЈ), (Z)-isomer], 7.38 [d, J = 8.6 Hz, 2 H; H-C(24ЈЈЈ,28ЈЈЈ),

(Z/E)-isomers], 7.46 [d, J = 8.2 Hz, 0.6 H; H-C(8ЈЈЈ,12ЈЈЈ), (E)-iso-

mer], 7.59 [d, J = 8.3 Hz, 0.6 H; H-C(9ЈЈЈ,11ЈЈЈ), (E)-isomer], 7.62

Eur. J. Org. Chem. 2015, 91–108

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105

D. M. Guldi, F. Diederich et al.

(200 °C, 0.4 mbar). R_f= 0.36 (SiO₂; cyclohexane/CH₂Cl₂, 2:8). H 2147 (w), 1803 (w), 1700 (w), 1601 (s), 1592 (s), 1495 (m), 1477

FULL PAPER

1

(m), 1394 (w), 1362 (s), 1337 (m), 1287 (m), 1246 (m), 1204 (m),

1168 (m), 1067 (w), 1000 (s), 946 (w), 930 (w), 899 (w), 881 (w),

859 (w), 822 (s), 797 (s), 765 (w), 733 (w), 715 (s) cm^–1. UV/Vis

(PhCN): λ_max(ε, m^–1cm^–1) = 604 (14600), 564 (25400), 432 nm

(646100); fluorescence (CHCl₃): λ_exc= 550 nm; λ_em= 595, 647 nm.

HRMS (MALDI, DCTB): m/z (%) = 1572.7845 (28), 1571.7826

(52), 1570.7817 (68), 1569.7831 (75), 1568.7845 (88), 1567.7854

(100), 1566.7811 (78) {[M]⁺, calcd. for C₁₀₇H₁₀₆N₈⁶⁴Zn⁺:

1566.7826}.

NMR [600 MHz, CDCl₃; assignment based on a COSY and a

HSQC spectrum and on reference compounds; E/Z ratio 10:1]: δ =

1.527, 1.533 [2s, 54 H; 6 CMe₃, (E/Z)-isomers], 1.85–2.06 [m, 1.1

H; H₂C(15ЈЈЈ,16ЈЈЈ,18ЈЈЈ,19ЈЈЈ,20ЈЈЈ,21ЈЈЈ), (Z)-isomer], 1.94 [dd, J

= 10.4, 4.8 Hz, 5.45 H; H₂C(16ЈЈЈ,18ЈЈЈ,21ЈЈ), (E)-isomer], 2.00 [dd,

J = 10.9, 4.8 Hz, 5.45 H; H₂C(15ЈЈЈ,19ЈЈЈ,20ЈЈЈ), (E)-isomer], 3.13

[s, 6 H; NMe₂, (E/Z)-isomers], 6.69 [d, J = 9.4 Hz, 0.18 H; H-

C(10ЈЈЈ,12ЈЈЈ), (Z)-isomer], 6.71 [d, J = 9.2 Hz, 1.82 H; H-

C(10ЈЈЈ,12ЈЈЈ), (E)-isomer], 6.83 [s, 0.91 H; H-C(1ЈЈЈ), (E)-isomer],

7.17 [s, 0.09 H; H-C(1ЈЈЈ), (Z)-isomer], 7.27 [d, J = 8.2 Hz, 0.18 H;

ZnP-S²-TCBD (؎)-9: A mixture of porphyrin (Ϯ)-54 (5 mg,

0.003 mmol) and TCNE (1.5 mg, 0.01 mmol) in CH₂Cl₂(2 mL)

was stirred at 23 °C for 13 h. Evaporation and MPLC (SiO₂; cyclo-

hexane/CH₂Cl₂, 4:6Ǟ0:1) gave a mixture of free-base and Zn por-

phyrin (Ϯ)-9. A solution of the crude material in CH₂Cl₂(3 mL)

was treated with a solution of Zn(OAc)₂·2H₂O (17 mg, 0.08 mmol)

in MeOH (1 mL), stirred at 23 °C for 17 h and the solvents evapo-

rated. A solution of the residue in CH₂Cl₂(20 mL) was washed

with water (2ϫ 15 mL), brine (15 mL), dried (Na₂SO₄), filtered,

and evaporated to afford (Ϯ)-9 (5 mg, 92%) as a purple solid. R_f=

0.30 (SiO₂; cyclohexane/CH₂Cl₂, 1:9). ¹H NMR (600 MHz, CDCl₃;

assignment based on a COSY and a HSQC spectrum): δ = 0.96–

1.02 [m, 1 H; H_ax-C(4ЈЈЈЈ)], 1.46–1.50 [m, 1 H; H_eq-C(4ЈЈЈЈ)], 1.56–

1.61 [m, 1 H; H_ax-C(8ЈЈЈЈ)], 1.65–1.71 [m, 3 H; H_ax-C(3ЈЈЈЈ,6ЈЈЈЈ),

H_eq-C(7ЈЈЈЈ)], 1.82–1.92 [m, 1 H; H_eq-C(3ЈЈЈЈ)], 1.97–2.06 [m, 3 H;

H-C(4ЈЈЈЈa), H_eq-C(6ЈЈЈЈ,7ЈЈЈЈ)], 2.14–2.22 [m, 1 H; H_eq-C(8ЈЈЈЈ)],

2.45 [td, J = 11.0, 3.0 Hz, 1 H; H-C(5ЈЈЈЈ)], 3.36 [br. t, J = 11.9 Hz,

1 H; H-C(8ЈЈЈЈa)], 3.41 [td, J = 13.5, 5.5 Hz, 1 H; H_ax-C(2ЈЈЈЈ)],

3.76 [dd, J = 14.1, 6.7 Hz, 1 H; H_eq-C(2ЈЈЈЈ)], 6.71 [d, J = 9.5 Hz,

2 H; H-C(3ЈЈЈ,5ЈЈЈ)], 6.78 [d, J = 9.5 Hz, 2 H; H-C(9ЈЈЈ,11ЈЈЈ)], 7.24

[d, J = 8.1 Hz, 2 H; H-C(2ЈЈЈЈЈ,6ЈЈЈЈЈ)], 7.64 [d, J = 8.2 Hz, 2 H; H-

C(3ЈЈЈЈЈ,5ЈЈЈЈЈ)], 7.79 [t, J = 1.9 Hz, 1 H; H-C(10Ј)], 7.798 [t, J =

1.8 Hz, 2 H; 2 H-C(4Ј)], 7.802 [d, J = 9.5 Hz, 2 H; H-C(8ЈЈЈ,12ЈЈЈ)],

7.82 [d, J = 9.4 Hz, 2 H; H-C(2ЈЈЈ,6ЈЈЈ)], 7.92 [d, J = 8.3 Hz, 2 H;

H-C(10ЈЈЈЈЈ,14ЈЈЈЈЈ)], 8.08 [d, J = 1.8 Hz, 1 H; H-C(8Ј,12Ј)], 8.09

[d, J = 1.8 Hz, 2 H; 2 H-C(2Ј,6Ј)], 8.23 [d, J = 8.4 Hz, 2 H; H-

C(11ЈЈЈЈЈ,13ЈЈЈЈЈ)], 8.96 [d, J = 4.6 Hz, 2 H; H-C(3,7)], 9.011 [s, 4

H; H-C(12,13,17,18)], 9.015 [d, J = 4.5 Hz, 2 H; H-C(2,8)] ppm.

¹³C NMR (150 MHz, CDCl₃; assignment based on a HSQC spec-

trum): δ = 22.39 [t; C(3ЈЈЈЈ)], 23.14 [t; C(4ЈЈЈЈ)], 25.03 [t; C(7ЈЈЈЈ)],

29.83 [t; C(8ЈЈЈЈ)], 31.91 (q, 18 C; 6 CMe₃), 35.04 [t; C(6ЈЈЈЈ)], 35.20

(s, 6 C; 6 CMe₃), 40.13 [t; C(2ЈЈЈЈ)], 40.28 (q, 2 C; NMe₂), 44.06 [d;

C(4ЈЈЈЈa)], 50.49 [d; C(5ЈЈЈЈ)], 64.43 [d; C(8ЈЈЈЈa)], 74.46 [s; C(1ЈЈ)],

75.08 [s; C(4ЈЈ)], 89.57 [s; C(8ЈЈЈЈЈ)], 90.23 [s; C(7ЈЈЈЈЈ)], 112.10 [d, 2

C; C(3ЈЈЈ,5ЈЈЈ)], 113.07 [d, 2 C; C(9ЈЈЈ,11ЈЈЈ)], 113.66, 113.74, 114.84,

115.01 (4s; 4 CϵN), 119.10 [s, 2 C; C(1ЈЈЈ,7ЈЈЈ)], 119.87 [s; C(9ЈЈЈЈЈ)],

120.97 [d, 3 C; 2 C(4Ј), C(10Ј)], 121.78 [s; C(4ЈЈЈЈЈ)], 122.54, 122.92

[2s; C(5,15)], 122.71 [s, 2 C; C(10,20)], 127.69 [br. s, 2 C;

C(2ЈЈЈЈЈ,6ЈЈЈЈЈ)], 129.73, 129.92 [2d, 4 C; C(8Ј,12Ј,10ЈЈЈЈЈ,14ЈЈЈЈЈ)],

129.80 [d, 4 C; 2 C(2Ј,6Ј)], 131.55 [d, 2 C; C(3,7)], 132.19 [d, 2

C; C(3ЈЈЈЈЈ,5ЈЈЈЈЈ)], 132.36, 132.47, 132.58 [3d; C(2,8,12,13,17,18)],

132.75, 132.90 [2d, 4 C; C(2ЈЈЈ,6ЈЈЈ,8ЈЈЈ, 12ЈЈЈ)], 134.52 [d, 2 C;

C(11ЈЈЈЈЈ,13ЈЈЈЈЈ)], 141.91 [s, 3 C; 2 C(1Ј), C(7Ј)], 143.35 [s;

C(12ЈЈЈЈЈ)], 144.51 [s; C(1ЈЈЈЈЈ)], 148.68 [s, 2 C; C(9Ј,11Ј)], 148.71 [s,

4 C; 2 C(3Ј,5Ј)], 149.89 [s, 2 C; C(4,6)], 150.53, 150.59, 150.67 [3s,

6 C; C(1,9,11,14,16,19)], 153.81 [s; C(10ЈЈЈ)], 154.31 [s; C(4ЈЈЈ)],

H-C(3ЈЈЈ,7ЈЈЈ), (Z)-isomer], 7.37 [d,

J = 8.3 Hz, 2 H; H-

C(23ЈЈЈ,27ЈЈЈ), (E/Z)-isomers], 7.52 [d, J = 8.3 Hz, 0.18 H; H-

C(4ЈЈЈ,6ЈЈЈ), (Z)-isomer], 7.62 [d, J = 8.3 Hz, 2 H; H-C(24ЈЈЈ,26ЈЈЈ),

(E/Z)-isomers], 7.67 [d, J = 9.1 Hz, 1.82 H; H-C(9ЈЈЈ,13ЈЈЈ), (E)-

isomer], 7.71 [d, J = 8.5 Hz, 1.82 H; H-C(4ЈЈЈ,6ЈЈЈ), (E)-isomer],

7.79 [t, J = 1.8 Hz, 1 H; H-C(10Ј), (E/Z)-isomers], 7.80 [t, J =

1.8 Hz, 2 H; 2 H-C(4Ј), (E/Z)-isomers], 7.92 [d, J = 8.2 Hz, 2.18

H; H-C(31ЈЈЈ,35ЈЈЈ), (E/Z)-isomers, and H-C(9ЈЈЈ,13ЈЈЈ), (Z)-iso-

mer], 8.07 [d, J = 8.2 Hz, 1.82 H; H-C(3ЈЈЈ,7ЈЈЈ), (E)-isomer], 8.09

[d, J = 1.8 Hz, 2 H; H-C(8Ј,12Ј), (E/Z)-isomers], 8.10 [d, J =

1.8 Hz, 4 H; 2 H-C(2Ј,6Ј), (E/Z)-isomers], 8.23 [d, J = 8.1 Hz, 2 H;

H-C(32ЈЈЈ,34ЈЈЈ), (E/Z)-isomers], 8.97 [d, J = 4.7 Hz, 2 H; H-C(3,7),

(E/Z)-isomers], 9.01 [s, 4 H; H-C(12,13,17,18), (E/Z)-isomers], 9.02

[d, J = 4.7 Hz, 2 H; H-C(2,8), (E/Z)-isomers] ppm. ¹³C NMR

[150 MHz, CDCl₃; assignment based on a HSQC and a HMBC

spectrum and on reference compounds; E/Z ratio 10:1]: δ [signals

of (E)-8]

= 28.85 [s; C(14ЈЈЈ)], 31.70, 32.05 [2 t, 6 C;

C(15ЈЈЈ,16ЈЈЈ,18ЈЈЈ,19ЈЈЈ,20ЈЈЈ,21ЈЈЈ)], 31.91 (q, 18 C; 6 CMe₃), 34.28

[s; C(17ЈЈЈ)], 35.20 (s, 6 C; 6 CMe₃), 40.22 (q, 2 C; NMe₂), 75.53

[s; C(CN)₂], 78.01 [s; C(3ЈЈ)], 89.38 [s; C(29ЈЈЈ)], 90.40 [s; C(28ЈЈЈ)],

110.68 [s; C(4ЈЈ)], 111.27 [d, 2 C; C(10ЈЈЈ,12ЈЈЈ)], 113.02 [s; C(5ЈЈЈ)],

114.63, 115.89 [2s; C(CN)₂], 118.66 [s; C(5ЈЈЈ)CN], 119.94 [s;

C(30ЈЈЈ)], 120.75 [s; C(8ЈЈЈ)], 120.96 [d, 3 C; 2 C(4Ј), C(10Ј)], 120.99

[s; C(25ЈЈЈ)], 122.66 [s; C(5)], 122.70 [s, 2 C; C(10,20)], 122.88 [s;

C(15)], 123.06 [s; C(2ЈЈ)], 125.74 [d, 2 C; C(23ЈЈЈ,27ЈЈЈ)], 129.73,

129.93, 130.01 [3d, 6 C; C(8Ј,12Ј,31ЈЈЈ,35ЈЈЈ,3ЈЈЈ,7ЈЈЈ)], 129.80 [d, 4

C; 2 C(2Ј,6Ј)], 131.59 [d, 2 C; C(3,7)], 131.75 [d, 2 C; C(24ЈЈЈ,26ЈЈЈ)],

132.20 [d, 2 C; C(4ЈЈЈ,6ЈЈЈ)], 132.34, 132.45, 132.58 [3d, 6 C;

C(2,8,12,13,17,18)], 133.29 [d, 2 C; C(9ЈЈЈ,13ЈЈЈ)], 134.50 [d, 2 C;

C(32ЈЈЈ,34ЈЈЈ)], 139.09 [s; C(2ЈЈЈ)], 141.32 [d; C(1ЈЈЈ)], 141.91 [s, 3 C;

2 C(1Ј), C(7Ј)], 143.23 [s; C(33ЈЈЈ)], 148.68 [s, 2 C; C(9Ј,11Ј)], 148.70

[s,

C(4,6)], 150.54, 150.57, 150.65 [3s,

153.77 [s; C(11ЈЈЈ)], 171.65 [s; C(1ЈЈ)] ppm;

(Z)-8] 28.85 [s; C(14ЈЈЈ)], 31.70, 32.05 [2 t,

4

C;

2

C(3Ј,5Ј)], 149.55 [s; C(22ЈЈЈ)], 149.93 [s,

C; C(1,9,11,14,16,19)],

[signals of

C;

2 C;

6

δ

=

6

C(15ЈЈЈ,16ЈЈЈ,18ЈЈЈ,19ЈЈЈ,20ЈЈЈ,21ЈЈЈ)], 31.91 (q, 18 C; 6 CMe₃), 34.28

[s; C(17ЈЈЈ)], 35.20 (s, 6 C; 6 CMe₃), 40.22 (q, 2 C; NMe₂), 79.94

[s; C(3ЈЈ)], 89.38 [s; C(29ЈЈЈ)], 90.40 [s; C(28ЈЈЈ)], 111.27 [d, 2 C;

C(10ЈЈЈ,12ЈЈЈ)], 112.15 [s; C(5ЈЈЈ)], 118.66 [s; C(5ЈЈЈ)CN], 119.94 [s;

C(30ЈЈЈ)], 120.96 [d, 3 C; 2 C(4Ј), C(10Ј)], 120.99 [s; C(25ЈЈЈ)],

122.66 [s; C(5)], 122.70 [s, 2 C; C(10,20)], 122.88 [s; C(15)], 125.74

[d, 2 C; C(23ЈЈЈ,27ЈЈЈ)], 129.07 [d, 2 C; C(3ЈЈЈ,7ЈЈЈ)], 129.73, 129.93

or 130.01 [2d, 4 C; C(8Ј,12Ј,31ЈЈЈ,35ЈЈЈ)], 129.80 [d, 4 C; 2 C(2Ј,6Ј)],

131.59 [d, 2 C; C(3,7)], 131.75 [d, 2 C; C(24ЈЈЈ,26ЈЈЈ)], 132.34,

132.45, 132.58 [3d, 6 C; C(2,8,12,13,17,18)], 132.73 [d, 2 C;

C(9ЈЈЈ,13ЈЈЈ)], 134.50 [d, 2 C; C(32ЈЈЈ,34ЈЈЈ)], 138.74 [d; C(1ЈЈЈ)],

141.91 [s, 3 C; 2 C(1Ј), C(7Ј)], 143.23 [s; C(33ЈЈЈ)], 148.68 [s, 2 C;

C(9Ј,11Ј)], 148.70 [s, 4 C; 2 C(3Ј,5Ј)], 149.55 [s; C(22ЈЈЈ)], 149.93

[s, 2 C; C(4,6)], 150.54, 150.57, 150.65 [3s, 6 C; C(1,9,11,14,16,19),

C(1ЈЈ,2ЈЈ,4ЈЈ,2ЈЈЈ,4ЈЈЈ,6ЈЈЈ,8ЈЈЈ,11ЈЈЈ), C(CN)₂] ppm and 2 CN miss-

165.17 [s; C(3ЈЈ)], 165.81 [s; C(2ЈЈ)] ppm. IR (ATR): ν = 2953 (m),

˜

2924 (m), 2858 (w, sh), 2216 (m), 2164 (w), 1600 (s), 1485 (s), 1441

(m), 1408 (m), 1380 (m), 1361 (m), 1347 (m), 1324 (m), 1287 (w),

1261 (m), 1247 (m), 1207 (s), 1183 (s), 1173 (s), 1128 (m), 1105 (w),

1068 (w), 999 (m), 946 (w), 930 (w), 899 (w), 882 (w), 860 (w), 819

(m), 797 (s), 732 (w), 716 (m), 624 (w) cm^–1. UV/Vis (PhCN): λ_max

(ε, m^–1cm^–1) = 605 (14600), 560 (27100), 488 (70200), 432 nm

ing (hidden by the noise or overlapping peaks). IR (ATR): ν = 3123

(w), 3062 (w), 2951 (m), 2906 (m), 2865 (m), 2218 (w), 2162 (w),

˜

106

www.eurjoc.org

Eur. J. Org. Chem. 2015, 91–108

Photoactive, Rigid Porphyrin Conjugates

(545700); fluorescence (CHCl₃): λ_exc= 550 nm; λ_em= 595, 646 nm.

HRMS (MALDI, DCTB): m/z (%) = 1602.8084 (27), 1601.8059

(50), 1600.8046 (67), 1599.806 (74), 1598.8068 (86), 1597.8075

(100), 1596.8043 (82) {[M]⁺, calcd. for C₁₀₇H₁₀₈N₁₀⁶⁴Zn⁺:

1596.8044}.

Acknowledgments

The work at ETH was supported by the Swiss National Science

Foundation and the ERC Advanced, grant number 246637 (“OP-

TELOMAC”). Support from The Free State of Bavaria “Solar

Technologies Go Hybrid” Initiative is acknowledged.. Michael So-

lar is acknowledged for the laborious mounting and testing of crys-

tal samples for X-ray diffraction measurements. The authors thank

Dr. B. Bernet for assistance in the spectral interpretations and Dr.

T. A. Reekie for proofreading the manuscript.

X-ray Analysis: ORTEP diagrams of all compounds except (Ϯ)-55

and ZnP-S¹-DCBD 5·7EtOH, for which X-ray data was collected

can be found in Section S5 in the Supporting Information. The

structures were solved by direct methods with SHELXS^[42]and re-

fined by full-matrix least-squares analysis (SHELXL),^[42]using the

OLEX2 software package.^[43]Data were corrected for absorption

effects using the multi-scan method (SADABS).

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X-ray Crystal Structure of (؎)-55: Single crystals were obtained by

slow evaporation of a solution of (Ϯ)-55 in CH₂Cl₂layered with

EtOH on top at 23 °C: C₂₀₆H₂₁₆N₁₂Zn₂; M_r= 2990.64; triclinic;

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¯

space group P1 (no. 2); crystal dimensions 0.18ϫ0.16ϫ0.03 mm ;

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=

¯

1766.71; triclinic; space group P1 (no. 2); crystal dimensions

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25.122(2) Å, α = 90.541(2)°, β = 104.656(2)°, γ = 113.593(2)°; V =

5098.5(8) Å³; Z = 2; ρ_calcd.= 1.151 gcm^–3; T = 100 K; Bruker

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Kappa Apex-II Duo diffractometer, Mo-K_αradiation;

λ =

0.71073 Å; μ = 0.298 mm^–1. 48926 reflections measured (3.24Յ

2θՅ 55.28°), 23487 unique (R_int= 0.0415, R_sigma= 0.0758) which

were used in all calculations. The final R₁was 0.0701 [IϾ2σ(I)]

and wR₂was 0.2250 (all data).

CCDC-992460 (for 20·MeOH), -992461 [for (Ϯ)-45·HCl], -992462

(for 21), -992463 (for 13), -992464 (for 11), -992465 (for 14),

-992466 [for (Z)-17], -992467 [for (E)-17·0.5CH₂Cl₂], -992468 [for

(Z)-16], -992469 [for (Ϯ)-55], -992470 (for ZnP-S¹-DCBD

5·7EtOH), and -1019032 (for 32) contain the supplementary crys-

tallographic data for this publication. These data can be obtained

free of charge from The Cambridge Crystallographic Data Centre

via www.ccdc.cam.ac.uk/data_request/cif.

UV/Vis Spectroscopy: Lambda 2 UV/Vis spectrophotometer (Per-

kin–Elmer); absorption maxima λ_maxgiven in nm.

Steady-State Fluorescence Spectroscopy: Data were recorded with

a Horiba–Jobin–Yvon Fluoromax 3 spectrophotometer; all spectra

were recorded in deaerated solutions at room temperature (298 K)

in a 1 cm quartz cuvette and were corrected for the instrument

response. For the determination of fluorescence quantum yields,

ZnTPP was used.

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Received: September 24, 2014

Published Online: November 12, 2014

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Article Doi

Systematic variation of cyanobuta-1,3-dienes and expanded tetracyanoquinodimethane analogues as electron acceptors in photoactive, rigid porphyrin conjugates

DOI: 10.1002/ejoc.201403252

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