Platinum(ii) and palladium(ii) complexes with electron-deficient: Meso -diethoxyphosphorylporphyrins: Synthesis, structure and tuning of photophysical properties by varying peripheral substituents

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S. M. Borisov, M. Konovalov, A. A. Sinelshchikova, Y. G. Gorbunova, A. Y. Tsivadze, M. Meyer, S. Christine

and A. Bessmertnykh-Lemeune, Dalton Trans., 2019, DOI: 10.1039/C9DT01577A.

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PAPER

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Eﬃcient extraction of sulfate from water using

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Platinum(II) and palladium(II) complexes with electron-deficient

meso-diethoxyphosphorylporphyrins: synthesis, structure and

tuning of photophysical properties by varying peripheral

substituents

Marina V. Volostnykh,^aSergey M. Borisov,*^bMikhail A. Konovalov,^a,cAnna A. Sinelshchikova,^a

Yulia G. Gorbunova,*^a,dAslan Yu. Tsivadze,^a,dMichel Meyer,^eChristine Stern,^eAlla G.

Bessmertnykh-Lemeune*^e

Received 00th January 20xx,

Accepted 00th January 20xx

DOI: 10.1039/x0xx00000x

A

series of electron-deficient platinum(II) and palladium(II) meso-(diethoxyphosphoryl)porphyrins, namely [10-

www.rsc.org/

(diethoxyphosphoryl)-5,15-bis(p-tolyl)porphyrinato]palladium(II)

(PdDTolPP),

{10-(diethoxyphosphoryl)-5,15-bis[p-

(methoxycarbonyl)phenyl]porphyrinato}palladium(II)

[PdD(CMP)PP],

[10-(diethoxyphosphoryl)-5,15-

dimesitylporphyrinato]palladium(II) (PdDMesPP), [5-(diethoxyphosphoryl)-10,15,20-trimesitylporphyrinato]palladium(II)

(PdTMesPP) and the corresponding platinum(II) compounds, were synthesized and structurally characterized in solution

by means of ¹H, ¹³C, ³¹P NMR spectroscopies and in the solid state by single crystal X-ray diffraction [PdDTolPP,

PdD(CMP)PP and PtD(CMP)PP]. Their optical and photophysical properties (UV−vis absorption, luminescence and

excitation spectra, phosphorescence quantum yields and lifetimes) were also investigated. The complexes under

investigation emit at room temperature in the near-infrared region (670−770 nm). Phosphorescence quantum yields of the

palladium(II) meso-phosphorylated porphyrins lie in the range of 3.4 to 5.8%, with lifetimes of 633 to 858 μs in

deoxygenated toluene solutions at room temperature. The corresponding platinum(II) complexes exhibit phosphorescence

quantum yields in the range of 9.2 to 11%, with luminescence decay times of 56 to 69 μs. Moreover, effective

homogeneous oxygen quenching and the good sensitivity in toluene (~155 Pa^–1s^–1) were observed for the platinum(II)

complexes with phosphorylporphyrins in solution. Investigations of the photostability of porphyrinylposphonates and

related complexes lacking a phosphoryl group in DMF under irradiation in air using a 400 W vis–NIR lamp demonstrated

that photobleaching is strongly dependent on the substituent at the periphery of the macrocycle. Platinum and palladium

trimesitylphosphorylporphyrins PdTMesPP and PtTMesPP exhibit a high photostability in DMF solution and seem to be the

most potentially interesting derivatives of the series for oxygen sensing in biological samples and the covalent

immobilization on solid supports to prepare sensing devices including optic fibers.

phosphorescence and large Stokes shifts ¹

useful applications in OLEDs ²photovoltaics,³as singlet oxygen

sensitizers for photodynamic therapy⁴and photocatalysis ⁵

as

well as labels in living

ells.^6–8Efficient quenching of their

phosphorescence by molecular oxygen enables the optical

oxygen sensing ^8–10

The quantitative measurement of dioxygen

. They have found

,

Introduction

Platinum(II) and palladium(II) porphyrins are very attractive

luminophores due to their strong room temperature

,

c

.

^a.Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of

Sciences, Leninsky pr. 31-4, Moscow, 119071, Russia. E-mail: yulia@igic.ras.ru

Institute of Analytical Chemistry and Food Chemistry, Graz University of

levels by these compounds relies on monitoring the changes of

either the emission intensity or the lifetime of the long-lived

triplet excited state induced by the interactions of the excited

b.

Technology, Stremayrgasse 9, A-8010 Graz, Austria

^c.Chemistry Department, Lomonosov Moscow State University, Leninskie Gory 1/3,

Moscow, 119991, Russia

chromophore with O₂molecules ^11,12

When phosphorescent

.

d.

compounds are used for oxygen sensing, their photostability is

of particular importance because the mechanisms of oxygen

signalling and chromophore photobleaching involve several

common processes. Reactive oxygen species (ROS: superoxide

anion radical or singlet oxygen) generated during the detection

process can react with the porphyrin molecules leading to

Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of

Sciences, Leninsky pr. 31, Moscow, 119991, Russia

Institut de Chimie Moléculaire de l'Université de Bourgogne (ICMUB), UMR 6302

e.

CNRS, Université Bourgogne Franche-Comté, 9 Avenue Alain Savary, BP 47870,

21078 Dijon Cedex, France

Electronic Supplementary Information (ESI) available: ¹H, ¹³C, and ³¹P NMR spectra,

MALDI-TOF and ESI-HR mass spectra of all prepared complexes, X-ray crystal data,

emission spectra and photophysical properties of the Pt and Pd porphyrinates,

photodegradation kinetic data. See DOI: 10.1039/x0xx00000x

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their degradation. Alternatively, the triplet state itself can be

involved in various photo-induced reactions.¹³These chemical

processes could impair the accurate determination of the

dioxygen concentration in the studied sample.

Results and discussion

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DOI: 10.1039/C9DT01577A

Synthesis and characterization of the Pt(II) and Pd(II)

complexes

Pt(II) and Pd(II) complexes with octaethylporphyrin (OEP)

are commonly used phosphorescent indicators among the

The phosphorescent Pt(II) and Pd(II) complexes with meso-

tetrapyrrolic compounds, since they possess high brightness ^14–

.

phosphorylated porphyrins [MR¹PP−MR⁴PP, with R¹= DTol, R²

=

D(CMP), R³= DMes, and R⁴= TMes; M = Pt(II) and Pd(II)] (Chart 1)

were prepared in three steps: formation of the zinc(II)

phosphorylated complexes, removal of Zn²⁺in acidic media, and

subsequent complexation with the appropriate metal cations. The

zinc(II) phosphorylporphyrins (ZnR¹PP−ZnR⁴PP) were obtained using

a described procedure,²⁹with subsequent treatment with HCl for

metal removing. For palladium(II) insertion, the synthetic procedure

was slightly modified^41–44by refluxing the solution of free-base

porphyrin with Pd(OAc)₂in acetonitrile instead of the CHCl₃/MeOH

mixture,⁴⁵in which reduction of Pd(OAc)₂by MeOH occurs.⁴⁶The

replacement of MeOH by acetonitrile enabled to obtain all targeted

complexes PdR¹PP−PdR⁴PP in nearly quantitative yields (85–100%),

although the reduction of palladium acetate is still observed to

some extend and an excess of the palladium salt should be

employed to achieve a complete complex formation.

16

However the stability of OEP complexes toward oxidative

degradation is quite low. It was shown that the presence of

electron-withdrawing groups (Br, CN, and NO₂) has

a

pronounced effect on the electro-chemical properties of

porphyrin rings,^17–19in particular, it makes them easily

reducible and difficult to oxidize relative to the unsubstituted

porphyrin. Therefore, for most applications Pt(II) and Pd(II)

complexes with halogen-substituted TPP ligands such as,

H₂F₂₀TPP

H₂F₂₈TPP

[5,10,15,20-tetra(pentaphenyl)porphyrin]

or

[3,4,7,8,12,13,17,18-octafluoro-5,10,15,20-

tetra(pentaphenyl)porphyrin], which are robust towards

oxidation, are successfully used ^11,20–22

π-Extended porphyrins

.

[e.g. tetrabenzoporphyrins (TBP)²³or tetranaphtoporphyrins

(TNP)²⁴] have also been intensively investigated in the field of

optical sensing materials. These compounds are excitable in

the red and NIR part of the electromagnetic spectrum and

possess a moderate to high brightness. For increasing the

Platinum(II) complexes with the phosphorylated porphyrins

PtR¹PP−PtR²PP were prepared according to a published

procedure,^47–49by reacting the corresponding free-base

porphyrins H₂R¹PP− H₂R⁴PP with PtCl₂in boiling benzonitrile

1

photostability of TBP and TNP to oxidation by O₂and other

ROS, the general strategy of incorporating electron- under argon. Complexes PtDTolPP and PtD(CMP)PP were

obtained in 85 and 70% yield, respectively. Surprisingly,

H₂DMesPP and H₂TMesPP were less reactive than H₂DTolPP

and H₂D(CMP)PP porphyrins. In spite of prolonged heating and

larger amounts of PtCl₂, PtDMesP could only be isolated in

18% yield. When complexation of H₂TMesPP was performed

under the same conditions, the starting compound was also

completely consumed, but the non-phosphorylated complex

PtTMesP was only isolated in low yield (15%), because of C−P

bond breaking. This side reaction has already been observed

withdrawing groups into the luminophore structure can also

be applied ^25,26

.

To the best of our knowledge, no photophysical data for

electron-deficient luminescent porphyrins substituted with

phosphoryl groups have been reported yet, because

convenient synthetic methods for their preparation were

developed only recently.^27–30Nevertheless, in a few studies it

was demonstrated that the introduction of one or more

electron-withdrawing P(O)(OR)₂(where R is an alkyl group)

groups directly attached to the porphyrin core at either  -

pyrrolic or meso- positions leads to positive shifts of the redox

potentials.^31–34It makes platinum(II) and palladium(II)

complexes with phosphorylporphyrins promising candidates

for the development of photostable oxygen sensing materials.

Moreover, meso-(diethoxyphosphoryl)porphyrinates are of

particular interest for the preparation of functional materials,

because their chemical modifications allow to obtain water-

for

porphyrinylphosphonate

diesters

under

acidic

conditions.^34,49When sodium acetate was added to the

reaction mixture to prevent a pH increase during the course of

the metal insertion, complexation proceeded smoothly even at

150 °C, affording the desired product in 89% yield.

The reference compounds, namely the Pt(II) and Pd(II)

complexes with the non-phosphorylated porphyrins

(MR¹P−MR⁴P, Chart 1), have not been described in the

literature so far, excepted for the PdDTolP complex that was

soluble derivatives²⁹and compounds with anchoring groups presented without full characterization by Quyang et al.⁵⁰as a

side product of the oxidative coupling of metal chlorins.

Herein, these complexes were obtained for the first time from

the free-base A₂-type porphyrins by the aforementioned

procedures for complexation (see the Experimental Section).

for subsequent grafting onto SiO₂surfaces and metal oxide

supports ^35–40

In this work we describe the synthesis, structural

characterization, and photophysical properties of the novel

phosphorescent meso-substituted Pt(II) and Pd(II)

.

phosphorylporphyrins. We examine the impact of introducing

an electron-withdrawing P(O)(OEt)₂group and aryl

substituents at meso-positions on the photophysical

characteristics of the platino- and palladoporphyrins, including

their photostability, as well as their sensitivity of molecular

oxygen detection in solution.

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compounds MR¹P−MR⁴P (Figures S59–S62, S67–S70 in the

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ESI), they are assigned to the P = O and ^DP^O−^IO^{: 10}v^.i¹b⁰r³a⁹t^/i^Co⁹n^Ds^To⁰¹f⁵t⁷h^7Ae

phosphoryl group (see the Experimental Section).

Single crystals for three complexes, namely PdDTolPP,

PdD(CMP)PP, and PtD(CMP)PP, were grown by slow diffusion

of n-hexane into a solution of the corresponding compound in

dichloromethane or chloroform. The structures were

determined by single crystal X-ray diffraction analysis

performed at 100 K. The summary of the crystallographic data

is presented in Table S1 (ESI). All complexes crystallized as

solvates in the triclinic P–1 space group. The asymmetric unit

includes one porphyrin molecule and one solvent molecule:

CH₂Cl₂for PdDTolPP, or CHCl₃for PdD(CMP)PP and

PtD(CMP)PP (Fig. 1). Platinum(II) and palladium(II) complexes

with the same porphyrin [PdD(CMP)PP and PtD(CMP)PP] are

isostructural with very close unit cell parameters (Fig. 1 and

Table S1, ESI). The molecular structures of the three

characterized complexes are typical for palladium(II) and

platinum(II) porphyrins. The metal centers have a square-

planar coordination geometry formed by four pyrrole nitrogen

atoms. The palladium and platinum atoms are nearly coplanar

with the N₄plane of the porphyrin core with a slight

displacement of 0.0124(9), 0.011(1), and 0.011(1) Å for

PdDTolPP, PdD(CMP)PP, and PtD(CMP)PP, respectively. The

mean metal–nitrogen distances are 2.016, 2.018, and 2.019 Å

for PdDTolPP, PdD(CMP)PP, and PtD(CMP)PP, respectively,

which is comparable to the metal–nitrogen distances reported

for other palladium(II) and platinum(II) porphyrins.^21,45,51,52The

molecular structure of the palladium complex with p-tolyl

substituted porphyrin PdDTolPP reveals a slightly ruffled

Chart 1 Chemical structures of the investigated phosphorylated Pt(II) and Pd(II)

porphyrins MR¹PP−MR⁴PP and of the corresponding reference compounds

MR¹P−MR⁴P.

All isolated platinum(II) and palladium(II) porphyrinates

1

were characterized in solution by H and ³¹P NMR and UV−vis

spectroscopies, as well as mass spectrometry (MALDI-TOF and

1

HR-ESI; see the Experimental Section and ESI). H, ¹³C, and ³¹P

NMR spectra of MR¹P−MR⁴P and MR¹PP−MR⁴PP in CDCl₃or

CDCl₃/CD₃OD mixture (2:1 v/v) were in accordance with the

proposed structures of the compounds (Figures S3–S6, S11–

S16, S19–S22, S27–S32 in the ESI). In the IR spectra of the

MR¹PP−MR⁴PP porphyrins (Figures S63–S66, S71–S74 in the

ESI), intense signals at ~ 950, ~1050, and ~1250 cm^–1were

observed in addition to the basic characteristic bands of the

porphyrin macrocycles and aryl substituents. Since these

features are absent in the spectra of the respective reference

Fig. 1 The asymmetric unit and respective view along the porphyrin plane of PdDTolPPCH₂Cl₂(left), PdD(CMP)PPCHCl₃(middle) and PtD(CMP)PPCHCl₃(right).

Thermal ellipsoids are at the 50% probability level.

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conformation of the macrocycle, in contrast to the virtually shifted by ~15 nm compared to those of the _Vp_iea_wll_Aa_rtd_ici_leu_Om_n(_liI_nI_e)

planar porphyrin core found for PdD(CMP)PP and phosphorylporphyrins. The maximum o^Df^Ot^Ih^{: 1}e^0.1S⁰o³r⁹e^/Ct⁹b^Da^T0n¹d⁵⁷⁷o^Af

PtD(CMP)PP. Perspective views along the porphyrin plane are these complexes is located at 395 nm, while that of the Q(1,0)

shown in Fig. 1. The largest deviations from the porphyrin N₄and Q(0,0) bands is centred at 511 and 546 nm, respectively.

mean plane are observed for the meso-carbon C(14) [0.268(3)

Å] and -carbon C(2) [0.248(4) Å] atoms in the PdDTolPP

crystal structure. In case of PdD(CMP)PP and PtD(CMP)PP, the

macroheterocycle is more flat and the largest deviations are

observed for the -carbon atoms closest to the phosphoryl

substituent [0.151(4) Å and 0.141(4) Å, respectively].

In all structures, the phosphoryl group is twisted with

respect to the N₄plane in such a way that the P = O bond lies

almost in the mean porphyrin plane, forming an

intramolecular C_β–HO hydrogen bond [PdDTolPP: C(3)O(1)

= 2.857 Å, angle C(3)–H(3)O(1) = 124.9; PdD(CMP)PP:

C(3)O(1)

= 2.851 Å, angle C(3)–H(3)O(1) = 127.2;

PtD(CMP)PP: C(3)O(1) = 2.857 Å, angle C(3)–H(3)O(1) =

127.2]. The ethoxy groups point out above and below the

porphyrin plane (Fig. 3). The torsion angles O(1)–P(1)–C(1)–

C(2) are 1.63, 14.1, and 13.8 for PdDTolPP, PdD(CMP)PP, and

PtD(CMP)PP, respectively. The P–O bond distances of

1.467(2)–1.472(2) Å (for P = O) and 1.568(2)–1.586(2) Å (for P–

O)

are

typical

for

meso-substituted

phosphorylporphyrins.^31,45,53The meso-phenyl rings are

twisted with respect to the porphyrin core by the following

angles: 60.0 and 78.9 for PdDTolPP, 85.6 and 63.7 for

PdD(CMP)PP, 84.3 and 63.7 for PtD(CMP)PP.

In all three structures, solvent molecules are involved in

intermolecular C–HO hydrogen bonds with phosphoryl

oxygen atoms. In addition, we identified ClO and ClC

contacts that are shorter than the sum of Bondi's van der

Walls radii⁵⁴(Table S8, ESI).

Fig.

2 UV–vis absorption spectra of the Pd(II) and Pt(II) phosphorylated

MR¹PP−MR²PP porphyrins and of the corresponding non-phosphorylated

MR¹P−MR²P counterparts in toluene.

The

crystal

packing

for

PdDTolPPCH₂Cl₂,

PdD(CMP)PPCHCl₃, and PtD(CMP)PPCHCl₃is discussed in

details in the ESI. It is formed mainly by  interactions

between porphyrin molecules (Figure S75, Table S9–10, ESI).

However, such interactions should not play any role for

photophysical measurements in solutions owing to the low

porphyrin concentrations (c ˂ 10^–5M) used for these

experiments.

Photophysical properties

The UV–vis absorption spectra of palladium(II) and platinum(II)

complexes with the phosphorylated porphyrins MR¹PP–MR⁴PP (Fig.

2, Table 1 and Table S11 in the ESI) were measured in dilute toluene

solutions at room temperature and compared to those of the

respective complexes formed with the non-phosphorylated A₂-type

porphyrins MR¹P–MR⁴P.

Changing aryl substituents from the electron-donating p-

tolyl to the electron-accepting p-(carbomethoxy)phenyl group

has only a little effect on the electronic spectra of the

porphyrins. The spectrum of both Pd(II) complexes [PdDTolPP

and PdD(CMP)PP] exhibit a Soret band at 409 nm and two

Q(1,0) and Q(0,0) bands at 522 and 556 nm, respectively. The

absorption maxima of the corresponding platinum(II)

complexes PtDTolPP and PtD(CMP)PP are hypsochromically

Fig. 3 Excitation (_em= _max(nm) and emission [_ex= λ_absQ(1,0) nm] spectra of

the Pd(II) (a) and Pt(II) (b) complexes in deoxygenated toluene at 298 K.

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Table 1 Photophysical properties of the phosphorylated PtR¹PP−PtR⁴PP porphyrins and of the non-phosphorylated PtR¹P−PtR⁴P counterparts in toluene

a

b

d

Dye

λ_abs(ε  10^–3)

λ_em

_em

 ^a

(s)

56

64

65

69

83

82

87

82

60

λ_em(77 K) ^c

(nm)

 (77 K) ^c

(μs)

94

E_T

(nm, M^–1cm^–1)

(nm)

674

670

672, 740(sh.)

671, 740(sh.)

650

(cm^–1)

15020

15100

15080

15150

15550

15800

15748

15773

-

PtTMesPP

PtDMesPP

PtDTolPP

PtD(CMP)PP

PtTMesP

PtDMesP

PtDTolP

PtD(CMP)P

PtF₂₀TPP^f

402 (136), 515 (12), 549 (9)

394 (211), 510 (13), 545 (21)

396 (257), 511 (17), 546 (26)

395 (325), 510 (28), 546 (41)

397 (184), 506 (18), 536 (9)

391 (241), 501 (19), 532 (16)

393 (143), 500 (24), 529 (18)

392 (206), 502 (18), 531 (14)

394, 540

11

9

11

9

13

15

16

9

666, 741

662, 734

663, 737

660, 735

643, 712

633, 701

635, 703

634, 700

-

117

119

122

122^e

133

137

-

637

639, 705(sh.)

632, 702(sh.)

648

^aMeasured in diluted toluene solutions at 298 °C deoxygenated by nitrogen bubbling. ^bThe absolute emission quantum yields were determined with an integrating

d

sphere. ^cMeasured in frozen glasses (toluene/tetrahydrofuran 4:6 v/v). Calculated from the emission spectra at 77 K. ^eNon mono-exponential signal with a much

longer component (1.56 ms) is present. ^fData are taken from ref.²⁰

Substitution in the meso-position of the porphyrin macrocycle type porphyrins. A narrow Q(0,0) emission peak [full width at

with an electron-withdrawing phosphoryl group results in half-maximum intensity (FWHM) = 35 nm] at 692 nm with a

bathochromic shifts of all absorption maxima. Thus, the Soret weak Q(1,0) band at 765 nm is observed for phosphorylated

band for the MR¹PP−MR⁴PP [M = Pt(II), Pd(II)] porphyrins was Pd(II) porphyrinates (Fig. 3a).

shifted by 3–5 nm and the Q bands by ~8–15 nm, in

Absolute quantum yields (_em) and luminescence lifetimes

comparison with the corresponding MR¹P−MR⁴P complexes () of the complexes were measured in deoxygenated toluene

that have no phosphoryl group. The intensity of the Q(0,0) solutions. For the palladium(II) meso-phosphorylporphyrins,

band for both Pt(II) and Pd(II) phosphorylated porphyrins is the observed _emand  values are 4.3% and 640 μs for

higher than that for the MR¹P−MR⁴P counterparts. This PdDTolPP, 5.8% and 633 μs for PdD(CMP)PP, 3.4% and 770 μs

behavior can be explained by the Gouterman four-orbital for PdDMesPP, and 4.1% and 858 μs for PdTMesPP. The

model,⁵⁵namely that electron-withdrawing phosphoryl group corresponding

at the meso-position may increase the a_1u−a_2uorbital energy hypsochromically shifted (~20−25 nm) [compared to Pd(II)

spacing and thus the intensity of the Q(0,0) transition. porphyrinates] narrow Q(0,0) emission peak (FWHM = 30 nm)

platinum(II)

complexes

exhibit

a

The Pt(II) and Pd(II) complexes with phosphorylated at 670 nm with a weak Q(1,0) band at 739 nm (Fig. 3b). They

porphyrins MR¹PP−MR⁴PP show moderate phosphorescence also possess 2.5–3-fold higher luminescence quantum yields

in deoxygenated solution at room temperature; their (9.2−11%) and 10-fold lower luminescence decay times [65,

photophysical data are listed in Table 1 and Table S11 (ESI). 69, 64, and 56 μs for PtDTolPP, PtD(CMP)PP, PtDMesPP and

Fig. 3 shows representative examples of normalized excitation PtTMesPP, respectively].

and emission spectra of the complexes under investigation

Furthermore, the emission spectra and decay times were

[MR¹PP and MR²PP, with M = Pt(II) and Pd(II)] together with recorded at 77 K, because the data obtained at low

those corresponding to the reference compounds [MR¹P and temperature are more accurate than those at 298 K due to the

MR²P, with M = Pt(II) and Pd(II)] in toluene at 298 K. There is a absence of competing processes (Table 1; Fig. S76–77 and

close resemblance between the excitation and ground-state Table S11 in the ESI). At low-temperature, the ratio of the

absorption spectra of all studied complexes. No fluorescence is emission intensities for the red to NIR emission peaks is much

detectable for the platinum(II) complexes and very little smaller for the dyes without a phosphoryl group (especially in

fluorescence (τ = 3.75 ns, _F˂ 0.1%) for the respective the case of platinum(II) complexes) than for the

palladium(II) complexes. In general, the emission profile of phosphorylated porphyrins. The obtained luminescence

phosphorylated Pt(II) and Pd(II) porphyrinates is nearly maxima at 77 K were used for estimation of the triplet excited-

identical to that of non-phosphorylated derivatives, but as can state energy (E_T), which are summarized in Table 1 and Table

be observed, the insertion of the electron-withdrawing S11 (ESI). Introduction of the electron-withdrawing group

phosphoryl group results in a bathochromic shift of the leads to a decrease in energy of the triplet excited state,

1

emission band by ca. 25−30 nm compared to the parent A₂- bringing the E_Tvalues of the dye closer to the energy of the

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훴_푔⁺

Journal Name

level of dioxygen (E = 13121 cm^–1).⁵⁶According to the data

PtD(CMP)PP, respectively]. This may be due to the slow

View Article Online

DOI: 10.1039/C9DT01577A

diffusion rates in solution of the bulky phosphorylated

obtained at 77 K, decay times of phosphorylated Pt(II) and

Pd(II) complexes are slightly reduced with respect of those

found for the corresponding MR¹P−MR⁴P diarylporphyrins.

Among the phosphorylated complexes, the following trend is

observed for the phosphorescence decay time  at 77 K:

MD(CMP)PP > MDTolPP > MDMesPP > MTMesPP. A similar

tendency is observed in the case of the luminescence quantum

yields determined at room temperature. Thus, the

combination of electron-withdrawing phosphoryl and p-

(carbomethoxy)phenyl substituents leads to the most

favorable photophysical parameters. The phosphorylation of

the porphyrin macrocycle results in reduction of both _emand

, which can be explained by the increased probability of the

non-radiative deactivation of the triplet excited state.

However, the obtained values are consistent with those known

for the most photostable palladium(II) and platinum(II)

porphyrinates (PtF₂₀TPP and PdF₂₀TPP),^20,57presented in the

literature, so metalloporphyrins presented in this work are

suitable for elaborating oxygen sensing devices.

porphyrins, or to the proximity of the E_Tvalue of the dyes with

¹훴_푔⁺

the

energy level of dioxygen. Nevertheless, the sensitivity

of the platinum(II) phosphorylated porphyrin complexes is

comparable to that of the commonly used PtOEP (210 Pa^–1s^–1

in toluene).²⁵Thus, it can be concluded that these dyes and

their derivatives are suitable indicators for developing optical

oxygen sensors.

Quenching by molecular oxygen in solution

Phosphorescence of all the investigated complexes is

effectively quenched in solution by molecular oxygen. Studies

were conducted with PdDTolPP, PdD(CMP)PP, PtDTolPP,

PtD(CMP)PP and their non-phosphorylated counterparts. The

results are presented in Fig. 4 and Fig. S78 (ESI). However, the

Pd(II) complexes show significantly lower luminescence

brightness and very high sensitivity even at low dioxygen

partial pressure in solution (pO₂), making precise

measurements challenging. Thus, the oxygen quenching

processes in solution were investigated in detail only for the

phosphorylated PtDTolPP and PtD(CMP)PP porphyrins, and for

the corresponding non-phosphorylated PtDTolP and

PtD(CMP)P counterparts.

Fig. 4 Luminescence spectra of PtDTolPP in toluene at 298 K in the absence and

in the presence of dioxygen (_ex= 511 nm) (a); Stern-Volmer plots for PtR¹,R²P

and PtR¹,R²PP in toluene (~7 x 10^–6M, 295 K) (b).

The dioxygen quenching of phosphorescence intensity (Fig.

4a) and decay time (Fig. 4b) can be interpreted in terms of the

Stern−Volmer relation, I₀/I = _ = 1 + k_q₀[O₂] = 1 + K_svpO₂,

where I₀and I denote the phosphorescence intensity in the

absence and the presence of dioxygen, respectively; ₀and 

correspond to the related decay lifetimes, k_qis the bimolecular

quenching constant; K_svis the Stern-Volmer constant.

As expected, all the studied complexes show good linearity

of _ as the function of pO₂between 0 and 1.95 kPa, which

indicates an effective homogeneous oxygen quenching in

solution. The calculated K_SVvalues for both platinum(II)

phosphorylated porphyrins PtDTolPP and PtD(CMP)PP are

similar [10.42 kPa^–1for PtDTolPP and 10.53 kPa^–1for

PtD(CMP)PP], but lower than the corresponding K_SVvalues for

the Pt(II) complexes lacking the phosphoryl group [15.08 kPa^–1

for PtDTolP and 12.36 kPa^–1for PtD(CMP)P]. This is mostly due

to the longer decay times of the latter. On the other hand, the

bimolecular quenching constants k_q= K_SV/τ₀are also slightly

smaller in the case of phosphorylated complexes [k_q= 173,

160, 156, 153 Pa^–1s^–1for PtDTolP, PtD(CMP)P, PtDTolPP, and

Photostability

Increasing interest in the development of oxygen sensors^10,58

and imaging agents,^7,8which should be stable under different

environmental conditions and useful for measurements in

biosamples and in vivo, explains the particular attention paid

on improving their photostability.^59–61While the photoinduced

degradation pathways of many organic fluorophores, such as

coumarins, rhodamines, and cyanines, have been explored to

some extent,¹³the reactions involved in the photobleaching of

porphyrins and phthalocyanines are less well understood.

Various porphyrins have been considered as potential

dioxygen sensors,^41,62–67and for some of the series the

influence of their peripheral substituents on the efficiency of

O₂detection has been investigated.^20,22,49,68However,

discussions of their photostability are commonly limited to a

general statement that the introduction of electron-

withdrawing substituents at the tetrapyrrolic macrocycle or at

peripheral aryl groups increases the photostability, as typically

6 | J. Name., 2012, 00, 1-3

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ARTICLE

observed for other organic fluorophores.^8,20,22To the best of be divided into two sets. The first group is formed by the

View Article Online

our knowledge, mechanisms of the photoinduced degradation mesityl-substituted porphyrins PtDMesP,

^{DOI: 10}P^.10tT³M^9/Ce⁹s^DP^T,⁰¹⁵a⁷n⁷d^A

of porphyrins in solution have still not been reported and data PtTMesPP, which are decomposed according to one

accumulated for photobleaching of phthalocyanines⁶⁹are also predominant pathway, like most of the previously studied

insufficient for suggesting any general reaction pathway.

In this work, we compared the photostability of different

organic phosphores.^13,70

porphyrinylphosphonate

diesters

(

MR¹PP−MR⁴PP)

and

analogous compounds (MR¹P−MR⁴P) that lack the phosphorous

substituent, to get a deeper insight on the influence of

peripheral substituents at the tetrapyrrolic macrocycle on the

photostability of porphyrins.

The photodegradation of all platinum(II) and palladium(II)

complexes was studied at first in DMF under the same

conditions. The porphyrin solutions (c = 5 M) were irradiated

at 25 °C in air using a 400 W lamp, which emits in the visible

and IR range (350–800 nm; Figure S79, ESI). The photoinduced

degradation kinetics of each tested compound was monitored

by absorption spectrophotometry at the maximum of the

Soret band until nearly or complete disappearance. The

electronic absorption spectrum of the resulting solution was

recorded at the end of the irradiation period. In all cases, the

final solution did not absorb visible light anymore. No further

efforts to identify the products were undertaken.

Although we have followed a commonly used methodology

for studying the photobleaching of organic compounds,⁷⁰it

should be stressed that these experiments allow only a semi-

quantitative comparison within a defined series of analogous

chromophores. Indeed, the degradation rate depends, among

other factors, on the concentration of the chromophore, the

photon absorption cross section, the intersystem crossing

efficiency, and to the triplet state lifetime. For comparison

purposes, the concentration and the total amount of absorbed

photons should be identical for all investigated substances,

which is in practice an unachievable situation as the light

absorptivity (() d) of even closely structurally related

molecules might significantly vary with the nature of

peripheral substituents born by the aromatic moiety.

Fig. 5. Photodegradation of platinum porphyrins (c = 5 M) in DMF at 25.0(5) °C

under vis–NIR irradiation with an Osram Powerstat HQI BT 400 W lamp. Colour

code: PtDTolP (brown), PtDTolPP (orange), PtD(CMP)PP (green), PtDMesP

(magenta), PtDMesPP (black), PtTMesP (blue), PtTMesPP (red).

The absorbance decline can be approximated by a single

exponential decay function. Moreover, no noticeable band

shift could be detected over time when the degradation of

PtTMesPP was monitored over the entire 350–600 nm range

(Fig. S80, ESI). The photobleaching rates of these compounds

can be compared by considering the pseudo-first-order rate

constants summarized in Table 2 derived by nonlinear least

squares adjustment of the experimental data after cutting the

induction period (Fig. S83–S85, ESI).

Table 2. Pseudo-first-order rate constants (k_obs) for the photodegradation of platinum

porphyrins in DMF a 25.0(5) °C

Compound

PtDMesP

PtTMesP

k_obs(s^–1)

k_obs/ k_obs(PtDMesP)

1

0.77

0.73

3.66  10^–5

2.83  10^–5

2.66  10^–5

The time course of the normalized absorbance decay

recorded over more than 80 h of continuous irradiation for

seven platinum porphyrinylphosphonate diesters is depicted in

Fig. 5. The inset of Fig. 5 clearly shows an induction period

during which the absorbance remains nearly constant over

about 25–35 min, followed by an abrupt multiphasic decrease

associated to photobleaching. The systematic observation of

an initiation phase strongly supports the photoinduced build-

up of radicals, which are presumably responsible for different

PtTMesPP

The introduction of a third mesityl substituent at the meso

position of the macrocycle increases the photostability of

platinum 5,15-dimesitylporphyrinate (PtDMesP), as PtTMesP

decomposes 1.3-fold more slowly than PtDMesP. Comparison

of the photobleaching rate constants of PtTMesP and

PtTMesPP reveals that the introduction of the

diethoxyphosphoryl group at meso position of the macrocycle

improves the photostability of the porphyrin only slightly, in

spite of the strong electron-withdrawing character of this

group.

degradation

processes

occurring

consecutively

or

simultaneously as suggested by the non-monotonous decay

curves of several studied compounds.

As shown in Fig. 5, the rate of the porphyrin

photobleaching depends strongly on the substituents attached

at the periphery of the tetrapyrrolic core. For example, the

extend of degradation during the first 100 min of irradiation

varies from 5 to 45%, depending on the porphyrin structure.

Moreover, the number and nature of peripheral substituents

have a most significant influence on the peculiar shape of the

kinetic traces. Accordingly, the compounds studied herein can

All the other platinum porphyrinates [PtDMesPP, PtDTolP,

PtDTolPP, and PtD(CMP)PP] belong to the second group of

studied complexes, for which the intricate decomposition

kinetics proceeds according to several pathways, as

highlighted by a first slowdown of the degradation rate some

minutes only after the initial boost, which is followed by a

second boost before the final rate deceleration. In addition,

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the degradation of PtDTolPP was also monitored over the significantly more reactive than the mesityl-substituted

View Article Online

entire 350–600 nm range (Fig. S81, ESI). Although no derivatives under the conditions employe^Dd^Oi^In^{: 1}t⁰h^.1is⁰³w^9/o^Cr⁹k^D. ^T01577A

noticeable band shift could be detected during the first 40 h of

Next, the photodegradation kinetics of the most stable

irradiation (_abs= 395, 511, and 546 nm), the Soret band palladium complexes PdTMesPP and PdDMesPP, together

undergoes a slight bathochromic shift of ca. 7 nm during the with the platinum porphyrin PtTMesP were also investigated

final stage of the degradation (40–116 h). This particular in toluene under identical irradiation conditions. In these

succession of fast and slow regimes hampers a quantitative experiments, the porphyrin concentrations slightly varied

analysis. All compounds belonging to this second category are (4.3−5.2 M) because the intensity of the absorbance at the

less stable than those of the first series, even if the electron- maximum of the Soret band was fixed to A = 1.0 (Fig. 7).

withdrawing diethoxyphosphoryl substituent is present at the

periphery of the macrocycle. Regarding the kinetics of

decomposition of PtDMesPP, PtDTolPP, and PtD(CMP)PP, we

can note that the replacement of both mesityl substituents by

p-methylphenyl

or

p-methoxycarbonylphenyl

groups

accelerates photobleaching. Also, the introduction of the

phosphorous substituent on PtDMesP and PtDTolP has

negative influence on the porphyrin degradation, at least in

the early stage of the process. Considering the electronic

effects of all these substituents, it can be concluded that the

electron-withdrawing character does not always increase the

photostability in this series of porphyrins, as claimed earlier for

porphyrins bearing pentafluorophenyl or other strongly

electron-withdrawing substituents.^1,8

Interestingly, the introduction of a diethoxyphosphoryl

group can change the photodegradation pathways in DMF, as

clearly revealed by the comparison of the bleaching curves of

PtDMesP and PtDMesPP. While the degradation of PtDMesP

can be considered in first approximation as a pseudo-first

order process, the decomposition of the phosphorylated

derivative involves several pathways. This might be reasonably

explained by the reactivity of the meso site at which a bulky

diethoxyphosphoryl group is attached. We have already

reported on the unusual C–P bond cleavage undergone by

porphyrinylphosphonate diesters under acidic conditions.^30,45

It seems that irradiation also accelerates the cleavage of C–P

bond.

Fig. 6 Photodegradation of platinum porphyrins (c = 5 M) in DMF at 25.0(5) °C

under vis–NIR irradiation with an Osram Powerstar HQI BT 400 W lamp. Colour

code: PdD(CMP)PP (dark green), PdDMesPP (black), PdTMesP (blue), PdTMesPP

(red), PdF₂₀TPP (green).

Absorbance decay curves of nearly sigmoidal shapes were

observed, presumably because of the occurrence of side reactions

involving photooxidation products of toluene and palladium

phosphrorylporphyrins. Nevertheless, it has been noted that the

trimesityl-substituted derivative PdTMesPP resists better to

photobleaching in toluene compared to PdDMesPP, in agreement

with the results obtained in DMF. Remarkably, the platinum

complex PtTMesP exhibit higher reactivity in toluene than the two

other investigated palladium porphyrins, whereas the reverse trend

was observed in DMF.

Another conclusion is that the compounds bearing mesityl

groups are the most stable ones, while an increasing number

of hydrogen atoms in either meso and/or in ortho positions of

meso aryl substituents accelerates the degradation of platinum

porphyrinates. These less stable macrocycles are decomposed

according to several pathways, presumably because these

meso and ortho hydrogen atoms take part in photo-induced

redox processes upon irradiation.

Next, the photostability of the PdD(CMP)PP, PdDMesPP,

PdTMesP, PdTMesPP palladium complexes and of the

reference compound PdF₂₀TPP was investigated under the

same conditions. The results are summarized in Fig. 6 and

compared to those of the corresponding platinum complexes

in Fig. S82 (ESI). For a given substitution pattern, the palladium

porphyrin is significantly less stable than the platinum

counterpart.

Within

the

palladium

series,

the

Fig. 7 Photodegradation of PdDMesPP (c = 4.6 M, black), PdTMesPP (c = 4.3

M, red), and PtTMesP (c = 5.2 M, blue) in toluene at 25.0(5) °C under vis–NIR

irradiation with an Osram Powerstar HQI BT 400 W lamp.

trimesitylphosphorylporphyrin PdTMesPP displays a higher

photostability compared to that of dimesityl- (PdDMesPP) and

bis(p-methoxycarbonyl)phosphorylporphyrin

PdD(CMP)PP.

Finally, the photostability of four palladium(II) [PdDTolP,

Surprisingly, PdF₂₀TPP, known for its high photostability,^1,8was

PdDTolPP, PdD(CMP)PP, and PdTPP (TPP

=

5,10,15,20-

8 | J. Name., 2012, 00, 1-3

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tetraphenylporphyrin)] (Fig. S86, ESI) and two platinum(II)

complexes [PtDTolPP and PtD(CMP)PP] (Fig. S87, ESI) were

investigated in air-saturated toluene solutions stored under day

light during 2 months. It was observed that the platinum(II)

derivatives PtDTolPP and PtD(CMP)PP are less stable compared to

their palladium(II) counterparts [PdDTolPP and PdD(CMP)PP], in

accordance with the aforementioned investigations performed in

the same solvent. Concomitantly to the absorbance decrease, new

absorption bands in the case of platinum(II) phosphorylated

porphyrinates were observed at higher wavelengths after two

months of exposure to sunlight. Moreover, the phosphorylated

derivatives PdDTolPP and PdD(CMP)PP degraded more slowly (25–

35%) than PdDTolP and PdTPP (75–90%). So, under these

conditions the introduction of the electron-withdrawing phosphoryl

group in the palladium(II) porphyrins seems to increase their

photostability, as it was observed for PtTMesP and PtTMesPP in

DMF.

with those known for the most photostable palladium(II) and

platinum(II) porphyrinates (PtF₂₀TPP and PdF₂₀TPP) reported

View Article Online

DOI: 10.1039/C9DT01577A

so far. Luminescent oxygen sensing properties of the Pt(II)

complexes were studied in solution. Our results demonstrate

effective homogeneous oxygen quenching and good

sensitivities, with bimolecular quenching constants (k_q) of ~155

Pa^–1s^–1in toluene for the platinum(II) phosphorylated

porphyrinates. It was also observed that the photostability of

porphyrinylphosphonates strongly depends on both the

solvent and the substituents occurring at the periphery of the

macrocycle. Among the studied compounds, platinum(II) and

palladium(II) trimesitylphosphrorylporphyrins PdTMesPP and

PtTMesPP exhibit a high photostability in air-saturated DMF

solution. Thus, phosphorylated metalloporphyrins presented in

this work are suitable for preparing dioxygen-sensing devices.

Experimental section

It turns out that the photobleaching rate of

phosphrorylporphyrins is highly solvent dependent. Likewise, the

central metal atom plays a crucial role, palladium complexes being

more reactive than platinum ones in DMF, why the trend is

reversed in toluene. Not surprisingly, the number and nature of

meso substituents have also a significant impact on the degradation

pathways and rates. Peripheral aromatic groups with ortho

hydrogen atoms are less protective than those possessing methyl

groups (e.g. mesityl) at the same position. Among the series of

General methods and characterization of compounds

Unless otherwise noted, all chemicals and starting materials

were obtained commercially from Acros® or Aldrich®, and

used without further purification. Solvents were dried using

standard procedures.⁷¹Chloroform (analytical grade) was

purchased from Merck and was distilled over CaH₂. DMA was

dried over molecular sieves. Toluene (HPLC-grade) was dried

over alumina cartridges using the solvent purification system

PureSolv PS-MD-5 model from Innovative Technology.

Analytical thin-layer chromatography (TLC) was carried out

using Merck silica gel 60 plates (precoated sheets, 0.2 mm

thick, with the fluorescence indicator F254). Column

chromatography purifications were carried out on silica gel

(MN Kieselgel 60, 63−200 m, Macherey-Nagel or Silica 60,

63–200 m, Aldrich). Gel permeation chromatography was

carried out using Bio-Beads^TMS-X3 Support (Bio-Rad

compounds

considered

in

this

work,

the

trimesitylporphyrinylphosphonate

diesters

PdTMesPP

and

PtTMesPP exhibit the highest photostability in air-saturated DMF

solution and toluene are presumably the most appealing

phosphorylated derivatives for dioxygen sensing in biological

samples or covalent immobilization on solid supports to prepare

sensing devices, including optical fibers.

1

Laboratories). H, ¹³C, and ³¹P NMR spectra were acquired on

Conclusions

Bruker Avance III (600 MHz), Avance III (500 MHz), or Avance II

(300 MHz) spectrometers. Chemical shifts are expressed in

parts per million (ppm), referenced on the  scale by using

residual non-deuterated solvent signals as internal standard

In conclusion, Pd(II) and Pt(II) complexes with electron-

deficient meso-(diethoxyphosphoryl)porphyrins have been

conveniently prepared and characterized. The complexes

under investigation emit at room temperature in the near-

infrared region (670–770 nm). Absorption and emission

spectrophotometric studies indicate that the incorporation of

diethoxyphosporyl group at the meso positions of the

porphyrin ring results in bathochromic shifts of the absorption

(~5 nm for Soret band and ~15 nm for Q bands) and the

emission (~25–30 nm) bands of complexes compared to those

of the parent A₂-type porphyrins. Phosphorescence quantum

yields of the palladium(II) meso-phosphorylated porphyrins lie

in the range of 3.4 to 5.8%, with lifetimes of 633 to 858 μs in

deoxygenated toluene solutions at room temperature. The

corresponding platinum(II) complexes exhibit quantum yields

in the range of 9.2 to 11%, with luminescence decay time

constants of 56 to 69 μs. The obtained values are consistent

1

for H and ¹³C NMR spectroscopies and external phosphoric

acid (H₃PO₄) for ³¹P NMR spectroscopy. The coupling constants

are expressed in units of frequency (Hz). MALDI-TOF mass-

spectra were obtained on a Bruker Ultraflex II LRF 2000 mass-

spectrometer in positive ion mode with a dithranol matrix.

Accurate mass measurements (HRMS) were recorded on a

Thermo LTQ Orbitrap XL apparatus equipped with electrospray

ionization (ESI) source. Solutions in CHCl₃/methanol (1:1) were

used for the analysis. The reported m/z values correspond to

the most intense peak of the isotopic pattern that were

simulated with the Xcalibur software (Thermo). FT-IR spectra

were collected at 4 cm^–1resolution on either a FT-IR Nexus

(Nicolet) or a Vertex 70v (Bruker) spectrometer equipped with

an universal micro-ATR (Pike) or an A225 (Bruker) ATR

sampling accessory, respectively. The UV−vis spectra were

recorded with a Varian Cary 5000 or a Shimadzu 2450

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Journal Name

and

(carbomethoxyl)phenyl]porphyrin

(diethoxyphosphoryl)-5,15-dimesitylporphyrin

and 5-(diethoxyphosphoryl)-10,15,20-trimesitylporphyrin

10-diethoxyphosphor_Vy_iel-_w5_A,1_rt5_icl-_eb_Ois_n[_lip_ne-

spectrophotometer by using rectangular quartz cells (Hellma,

100-QS, 45 x 12.5 x12.5 mm, light path 10 mm, volume 3.5 mL)

or a cylindrical quartz cell (Hellma, 121.000, light path 1 mm,

volume 0.28 mL).

The measurements were performed at the Shared Facility

Centers of the Institute of Physical Chemistry and

Electrochemistry, RAS, and at the "Plateforme d'Analyses

Chimiques et de Synthèse Moléculaire de l'Université de

Bourgogne - Pôle Chimie Moléculaire", the technological

platform for chemical analysis and molecular synthesis

(http://www.wpcm.fr).

[H_DOD_I(_:C₁M_0.1P₀)₃P₉P_/C]₉, _DT0151₇₇0_A-

2

(H₂DMesPP),

(H₂TMesPP) were prepared according to the published

procedures.²⁹

General procedure for preparation of Pd(II) complexes. A

solution of the free-base porphyrin H₂R¹P–H₂R⁴P or H₂R¹PP–

H₂R⁴PP in a CHCl₃/CH₃CN mixture was stirred and heated.

During refluxing, Pd(OAc)₂(4 equiv.) was added into the flask.

The reaction mixture was further stirred until complete

conversion of starting porphyrin. The degree of consumption

of the porphyrin was monitored by MALDI-TOF mass-

spectrometry and UV–vis spectroscopy. After cooling to room

temperature, the solvent was removed under reduced

pressure. The residue was purified by column chromatography

on silica gel to afford PdR¹P–PdR⁴P or PdR¹PP–PdR⁴PP.

X-ray crystallography

Single crystals of PdDTolPPCH₂Cl₂were obtained by slow

diffusion of n-hexane into a solution of the Pd(II) complex in

dichloromethane. Single crystals of PdD(CMP)PPCHCl₃and

PtD(CMP)PPCHCl₃were grown by slow diffusion of n-hexane

into solutions of the corresponding Pd(II) and Pt(II) complexes

in chloroform. Crystals mounted onto a glass needle using

silica oil, were cooled to the data collection temperature of

100 K. X-ray diffraction experiments for single crystals were

performed on a Bruker Kappa Apex II automatic four-circle

diffractometer equipped with an area detector (Mo K_αsealed-

tube X-ray source, λ = 0.71073 Å, graphite monochromator).

The unit cell parameters were refined over whole dataset

using SAINT-Plus.⁷²The experimental reflection intensities

were corrected for absorption using the SADABS program.⁷³

The structures were solved with the ShelXT⁷⁴program and

refined by the full-matrix least-squares method (SHELXL-

2014⁷⁵) on F²over the whole dataset in the anisotropic

approximation for all nonhydrogen atoms, both routines being

implemented in the Olex2 environment.⁷⁶The H atoms were

placed in the geometrically calculated positions with the

isotropic temperature factors set at 1.2 times (CH groups) or

1.5 times (CH₃group) the equivalent isotropic temperature

factor of their bonded C atoms. Table S1 (ESI) lists the

crystallographic characteristics and details of the diffraction

experiments.

[5,15-Bis(p-tolyl)porphyrinato]palladium(II)

(PdDTolP)

was prepared from 20 mg (0.041 mmol) of H₂DTolP and 37 mg

(0.163 mmol) of Pd(OAc)₂dissolved in 11 mL of a CHCl₃/CH₃CN

(80:20 v/v) mixture that was refluxed for 15 min. The resulting

solid was purified by column chromatography on silica gel

using CH₂Cl₂as eluent to give PdDTolP as a pink purple

1

crystalline powder (25.4 mg, 100%). H NMR (600 MHz, CDCl₃,

25 °C): δ_H2.73 (s, 6H, Ph-CH₃), 7.59 (d, ³J_H,H= 7.6 Hz, 4H, m-Ph),

8.10 (d, ³J_H,H= 7.8 Hz, 4H, o-Ph), 9.04 (d, ³J_H,H= 4.7 Hz, 4H, Hβ),

9.28 (d, ³J_H,H= 4.7 Hz, 4H, Hβ), 10.26 (s, 2H, H_meso). MS (MALDI-

TOF): m/z = 594.08 ([M]⁺, calcd. for C₃₄H₂₄N₄Pd m/z = 594.10).

HRMS (ESI): m/z = 594.10468 ([M]⁺, calcd. for C₃₄H₂₄N₄Pd m/z

594.10303). UV–vis [toluene; λ_max, nm (log ε)]: 406 (5.50), 514

(4.23), 544 (3.96). IR (neat, cm^–1): ν_max2952 (w), 2914 (m),

2849 (m), 1729 (m), 1537 (w), 1509 (w), 1457 (w), 1418 (w),

1391 (w), 1376 (w), 1335 (w), 1302 (w), 1234 (w), 1216 (w),

1194 (w), 1179 (m), 1102 (w), 1068 (m), 1046 (m), 1006 (s),

944 (w), 901 (w), 853 (s), 797 (m), 779 (s), 721 (s), 693 (s), 586

(w), 554 (w).

{5,15-Bis[p-(methoxycarbonyl)phenyl]porphyrinato}palla-

dium(II) [PdD(CMP)P] was prepared from 20 mg (0.035 mmol)

of H₂D(CMP)P and 31 mg (0.138 mmol) of Pd(OAc)₂dissolved

in 9 mL of a CHCl₃/CH₃CN (80:20 v/v) mixture. The reaction

mixture was refluxed for 15 min. The resulting solid was

purified by column chromatography on silica gel using CH₂Cl₂

as eluent to give PdD(CMP)P as a pink purple crystalline

X-ray diffraction experiments were performed at the

Center for Shared Use of Physical Methods of Investigation at

the Frumkin Institute of Physical Chemistry and

Electrochemistry, RAS.

Atomic coordinates have been deposited in the Cambridge

Crystallographic Data Centre [CCDC deposition codes are

1904438 for PdDTolPP, 1904436 for PdD(CMP)PP, 1904437 for

PtD(CMP)PP] and can be obtained on request at

www.ccdc.cam.ac.uk/data_request/cif.

1

powder (19.2 mg, 83%). H NMR (600 MHz, CDCl₃, 25 °C): δ_H

4.14 (s, 6H, Ph-COOCH₃), 8.31 (d, ³J_H,H= 8.3 Hz, 4H, o-Ph), 8.48

(d, ³J_H,H= 8.3 Hz, 4H, m-Ph), 8.96 (d, ³J_H,H= 4.7 Hz, 4H, Hβ), 9.32

(d, ³J_H,H= 4.8 Hz, 4H, Hβ), 10.32 (s, 2H, H_meso). MS (MALDI-TOF):

m/z = 682.11 ([M]⁺, calcd. for C₃₆H₂₄N₄O₄Pd m/z = 682.08).

HRMS (ESI): m/z = 682.08240 ([M]⁺, calcd. for C₃₆H₂₄N₄O₄Pd

m/z = 682.08269). UV–vis [toluene; λ_max, nm (log ε)]: 406 (4.97),

514 (3.94), 544 (3.54). IR (neat, cm^–1): ν_max2917 (w), 2849 (w),

1715 (s, C=O), 1603 (w), 1540 (w), 1507 (w), 1457 (w), 1427

(w), 1397 (w), 1337 (w), 1305 (w), 1270 (br, m), 1194 (w), 1176

(w), 1152 (w), 1107 (m), 1095 (m), 1071 (m), 1009 (s), 969 (w),

919 (w), 874 (w), 847 (s), 821 (m), 780 (s), 754 (s), 723 (s), 693

(s), 638 (w), 592 (w), 569 (w), 554 (m).

Synthesis

Dipyrromethane was prepared by the published

procedure.^77,78Non-phosphorylated free-base A₂-type

porphyrins, namely 5,15-bis(p-tolyl)porphyrin (H₂DTolP),^79,80

5,15-bis[p-(carbomethoxyl)phenyl]porphyrin [H₂D(CMP)P],⁸¹

[10-(Diethoxyphosphoryl)-5,15-bis(p-

5,15-dimesitylporphyrin

(H₂DMesP),^82,83

and

5,10,15-

tolyl)porphyrinato]palladium(II) (PdDTolPP) was prepared

from 7 mg (0.011 mmol) of H₂DTolPP and 10 mg (0.045 mmol)

of Pd(OAc)₂dissolved in 3 mL of a CHCl₃/CH₃CN (80:20 v/v)

mixture. The reaction mixture was refluxed for 15 min. The

resulting solid was purified by column chromatography on

trimesitylporphyrin (H₂TMesP),⁸⁴were obtained by literature

methods.

The starting free-base phosphorylated porphyrins 10-

(diethoxyphosphoryl)-5,15-bis(p-tolyl)porphyrin

(H₂DTolPP)

10 | J. Name., 2012, 00, 1-3

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ARTICLE

silica gel using a CHCl₃/n-hexane (1:1 v/v) as eluent to give (4.31), 546 (3.95). IR (neat, cm^–1): ν_max2953 (m), 2920 (s), 2852

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PdDTolPP as a pink purple crystalline powder (8.5 mg, 100%). (m), 1717 (br, w), 1609 (w), 1571 (w), 1536 (w), 1456 (br, m),

DOI: 10.1039/C9DT01577A

¹H NMR (600 MHz, CDCl₃/CD₃OD 2:1 v/v, 25 °C): δ_H1.16 (t, ³J_H,H1396 (w), 1375 (m), 1338 (w), 1320 (w), 1301 (w), 1260 (w),

= 7.0 Hz, 6H, OCH₂CH₃), 2.53 (s, 6H, Ph-CH₃), 3.98–4.05 (m, 2H, 1242 (w), 1183 (w), 1165 (w), 1144 (w), 1060 (m), 1036 (w),

3

OCH₂CH₃), 4.24–4.31 (m, 2H, OCH₂CH₃), 7.39 (d, J_H,H= 7.6 Hz, 1011 (s), 970 (w), 912 (w), 853 (m), 835 (m), 787 (m), 729 (m),

3

4H, m-Ph), 7.83 (d, J_H,H= 7.7 Hz, 4H, o-Ph), 8.70 (d, J_H,H= 4.7 721 (m), 698 (m), 568 (w).

3

Hz, 2H, Hβ), 8.78 (d, J_H,H= 5.1 Hz, 2H, Hβ), 9.02 (d, J_H,H= 4.6

(5,15,20-Trimesitylporphyrinato)palladium(II) (PdTMesP)

3

Hz, 2H, Hβ), 10.02 (s, 1H, H_meso), 10.08 (d, J_H,H= 5.1 Hz, 2H, was prepared from 19 mg (0.029 mmol) of H₂TMesP and 104

Hβ). ³¹P{¹H} NMR (600 MHz, CDCl₃/MeOD 2:1 v/v, 25 °C): δ_Pmg (0.463 mmol) of Pd(OAc)₂in 8 mL of a CHCl₃/CH₃CN (50:50

23.17. MS (MALDI-TOF): m/z = 730.17 ([M]⁺, calcd. for v/v) mixture. The reaction mixture was refluxed for 96 h. The

C₃₈H₃₃N₄O₃PPd m/z = 730.13). HRMS (ESI): m/z = 730.13491 resulting solid was purified by silica gel column

([M]⁺, calcd. for C₃₈H₃₃N₄O₃PPd m/z = 730.13196). UV–vis chromatography and gel permeation chromatography using

[toluene; λ_max, nm (log ε)]:410 (5.32), 523 (4.28), 557 (4.37). IR CH₂Cl₂and CHCl₃as eluent, respectively, to give PdTMesP as

(neat, cm^–1): ν_max2976 (w), 2918 (w), 1608 (w), 1539 (w), 1468 an orange crystalline powder (7 mg, 32%). H NMR (600 MHz,

1

(w), 1433 (w), 1391 (w), 1369 (w), 1329 (w), 1295 (w), 1249 CDCl₃, 25 °C): δ_H1.84 (s, 12H, o-CH₃), 1.85 (s, 6H, o-CH₃), 2.63

(m), 1214 (w), 1179 (w), 1160 (w), 1089 (w), 1067 (m), 1043 (s, 3H, p-CH₃), 2.65 (s, 6H, p-CH₃), 7.27 (br s, 2H, m-Ph), 7.30

=

3

[PdD(CMP)PP] was prepared from 70 mg (0.098 mmol) of o-CH₃), 21.72 (2C, p-CH₃), 106.04 (1C, meso-C), 119.06 (2C,

H₂D(CMP)PP and 88 mg (0.392 mmol) of Pd(OAc)₂dissolved in meso-C), 119.71 (1C, meso-C), 127.75 (2C, m-C_Mes), 127.80 (4C,

25 mL of a CHCl₃/CH₃CN (80:20 v/v) mixture. The reaction m-C_Mes), 130.06 (2C, β-C), 130.22 (4C, β-C), 131.25 (2C, β-C),

mixture was refluxed for 15 min. The resulting solid was 137,70 (2C, C_Mes), 137.75 (2C, C_Mes), 137.93 (2C, C_Mes), 138.06

purified by column chromatography on silica gel using a (2C, C_Mes), 139.32 (4C, C_Mes), 140.87 (2C, α-C), 141.00 (2C, α-C),

CHCl₃/MeOH (100:1 v/v) mixture as eluent to give 141.14 (2C, α-C), 141.29 (2C, α-C). HRMS (ESI): m/z =

PdD(CMP)PP as a pink purple crystalline powder (70.4 mg, 768.24534 ([M]⁺, calcd. for C₄₇H₄₂N₄Pd m/z = 768.24388). UV–

1

91%). H NMR (600 МHz, CDCl₃/CD₃OD 2:1 v/v, 25 °C): δ_H1.17 vis [toluene; λ_max, nm (log ε)]: 412 (5.40), 519 (4.37), 550

3

(t, J_H,H= 7.0 Hz, 6H, OCH₂CH₃), 3.93 (t, 6H, PhCOOCH₃), 4.01– (3.68). IR (neat, cm^–1): ν_max2914 (w), 2851 (w), 1726 (w), 1609

4.05 (m, 2H, OCH₂CH₃), 4.27–4.31 (m, 2H, OCH₂CH₃), 8.03 (d, (w), 1570 (w), 1538 (w), 1447 (br, m), 1388 (w), 1373 (w), 1341

³J_H,H= 8.0 Hz, 4H, o-Ph), 8.25 (d, ³J_H,H= 8.0 Hz, 4H, m-Ph), 8.58 (w), 1332 (w), 1305 (w), 1242 (w), 1214 (w), 1184 (w), 1166

3

(d, J_H,H= 4.7 Hz, 2H, Hβ), 8.68 (d, J_H,H= 5.2 Hz, 2H, Hβ), 9.01 (w), 1152 (w), 1065 (m), 1034 (w), 1010 (s), 952 (w), 902 (w),

3

(d, J_H,H= 4.7 Hz, 2H, Hβ), 10.01 (s, 1H, H_meso), 10.12 (d, J_H,H

=

864 (w), 843 (m), 834 (m), 796 (m), 776 (m), 755 (m), 718 (m),

5.2 Hz, 2H, Hβ). ³¹P{¹H} NMR (600 MHz, CDCl₃/CD₃OD 2:1 v/v, 692 (m), 557 (w).

25 °C): δ_P22.55. MS (MALDI-TOF): m/z = 818.28 ([M]⁺, calcd.

[10-(diethoxyphosphoryl)-5,15-

for C₄₀H₃₃N₄O₇PPd m/z = 818.11). HRMS (ESI): m/z = 818.11239 dimesitylporphyrinato]palladium(II)

(PdDMesPP)

was

([M]⁺, calcd. for C₄₀H₃₃N₄O₇PPd m/z = 818.11162), 841.09803 prepared from 25 mg (0.037 mmol) of H₂DMesPP and 66 mg

([M+Na]⁺, calcd. for C₄₀H₃₃N₄O₇PPdNa m/z 841.10139). UV–vis (0.295 mmol) of Pd(OAc)₂in 9 mL of a CHCl₃/CH₃CN (50:50 v/v)

[toluene; λ_max, nm (log ε)]:410 (5.31), 523 (4.25), 557 (4.31). IR mixture. The reaction mixture was refluxed for 2 h. The

(neat, cm^–1): ν_max2984 (w), 2917 (w), 2850 (w), 1719 (s, C=O), resulting solid was purified by silica gel column

1607 (m), 1541 (w), 1433 (m), 1401 (w), 1391 (w), 1308 (w), chromatography using a CH₂Cl₂/MeOH (95:5 v/v) mixture as

1274 (s), 1253 (s), 1217 (w), 1179 (w), 1162 (w), 1109 (m), eluent to give PdDMesPP as a pink crystalline powder (27 mg,

1097 (m), 1072 (w), 1044 (w), 1011 (s), 965 (s), 893 (m), 864 97%). ¹H NMR (600 MHz, CDCl₃, 25 °C): δ_H1.38 (t, ³J_H,H= 7.0 Hz,

(m), 822 (w), 785 (m), 761 (s), 729 (s), 710 (s), 694 (m), 585 6H, OCH₂CH₃), 1.83 (s, 12H, o-CH₃), 2.66 (s, 6H, p-CH₃), 4.21–

(m), 565 (m), 551 (m).

4.29 (m, 2H, OCH₂CH₃), 4.51–4.59 (m, 2H, OCH₂CH₃), 7.32 (br s,

(5,15-Dimesitylporphyrinato)palladium(II) (PdDMesP) was 4H, m-Ph), 8.75 (d, ³J_H,H= 4.6 Hz, 2H, Hβ), 8.83 (d, ³J_H,H= 5.1 Hz,

3

prepared from 15 mg (0.027 mmol) of H₂DMesP and 98 mg 2H, Hβ), 9.18 (d, J_H,H= 4.6 Hz, 2H, Hβ), 10.16 (s, 1H, H_meso),

(0.437 mmol) of Pd(OAc)₂in 8 mL of a CHCl₃/CH₃CN (50:50 v/v) 10.38 (d, J_H,H= 5.1 Hz, 2H, Hβ). ³¹P{¹H} NMR (600 MHz, CDCl₃,

3

mixture. The reaction mixture was refluxed for 96 h. The 25 °C): δ_P22.59. ¹³C{¹H} NMR (150 MHz, CDCl₃, 25 °C): δ_c16.48

resulting solid was purified by silica gel column (d, ²J_C,_P= 7.2 Hz, 2C, OCH₂CH₃), 21.49 (2C, p-CH₃), 21.55 (4C, o-

2

chromatography and gel permeation chromatography using CH₃), 62.77 (d, J_C,_P= 4.4 Hz, 2C, OCH₂CH₃), 102.03 (d, J_C,_P=

CH₂Cl₂and CHCl₃as eluents, respectively, to give PdDMesP as 185.6 Hz, 1C, meso-C), 109.34 (2C, meso-C), 120.27 (1C, meso-

an orange crystalline powder (6 mg, 34%). H NMR (600 MHz, C), 127.90 (4C, m-C_Mes), 129.99 (2C, β-C), 131.48 (2C, β-C),

1

CDCl₃, 25 °C): δ_H1.81 (s, 12H, o-CH₃), 2.65 (s, 6H, p-CH₃), 7.31 132.21 (2C, β-C), 133.11 (2C, β-C), 137.61 (2C, C_Mes), 138.01

3

(br s, 4H, m-Ph), 8.84 (d, J_H,H= 4.6 Hz, 4H, Hβ), 9.24 (d, J_H,H

=

(2C, C_Mes), 139.13 (4C, C_Mes), 140.49 (2C, α-C), 140.74 (2C, α-C),

4.6 Hz, 4H, Hβ), 10.20 (s, 2H, H_meso). ¹³C{¹H} NMR (150 MHz, 142.18 (2C, α-C), 144.21 (d, J_C,_P= 18.3 Hz, 2C, α-CP). HRMS

CDCl₃, 25 °C): δ_c21.50 (2C, p-CH₃), 21.55 (4C, o-CH₃), 106.49 (ESI): m/z = 787.19982 ([M+H]⁺, calcd. for C₄₂H₄₂N₄O₃PPd m/z =

(2C, meso-C), 118.91 (2C, meso-C), 127.84 (4C, m-C_Mes), 130.27 787.20239), 809.18205 ([M+Na]⁺, calcd. for C₄₂H₄₁N₄O₃PPdNa

(4C, β-C), 131.42 (4C, β-C), 137.78 (2C, C_Mes), 137.85 (2C, C_Mes), m/z = 809.18433). UV–vis [toluene; λ_max, nm (log ε)]: 408 (5.34),

139.30 (4C, C_Mes), 141.04 (4C, α-C), 141.09 (4C, α-C). HRMS 522 (4.23), 555 (4.33). IR (neat, cm^–1): ν_max2919 (w), 2851 (w),

(ESI): m/z = 650.16779 ([M]⁺, calcd. for C₃₈H₃₂N₄Pd m/z = 1730 (w), 1608 (w), 1561 (w), 1539 (w), 1476 (w), 1436 (br, m),

650.16563). UV–vis [toluene; λ_max, nm (log ε)]: 405 (5.33), 514 1388 (w), 1374 (w), 1327 (w), 1295 (w), 1250 (m), 1217 (w),

2

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J. Name., 2013, 00, 1-3 | 11

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1165 (w), 1086 (w), 1063 (m), 1043 (m), 1011 (s), 954 (br, m), HRMS (ESI): m/z = 683.16445 ([M]⁺, calcd. for C₃₄H₂₄N₄Pt m /z =

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883 (m), 853 (m), 834 (w), 800 (m), 782 (m), 736 (m), 725 (m), 683.16460). UV–vis [toluene; λ_max, nm (log ε)]: 393 (5.16), 502

DOI: 10.1039/C9DT01577A

713 (m), 695 (m), 600 (m), 578 (w), 560 (m), 538 (m).

(4.38), 531 (4.25). IR (neat, cm^–1): ν_max2954 (w), 2916 (w),

2850 (w), 1729 (w), 1541 (w), 1509 (w), 1455 (w), 1395 (w),

was 1341 (w), 1326 (w), 1308 (m), 1179 (w), 1103 (w), 1069 (m),

[10-(diethoxyphosphoryl)-5,15,20-

trimesitylporphyrinato]palladium(II)

(PdTMesPP)

prepared from 24 mg (0.030 mmol) of H₂TMesPP and 54 mg 1042 (w), 1012 (s), 943 (w), 897 (w), 854 (s), 799 (m), 778 (s),

(0.241 mmol) of Pd(OAc)₂in 8 mL of a CHCl₃/CH₃CN (50:50 v/v) 721 (s), 693 (s), 625 (w), 615 (w), 590 (w), 568 (w), 554 (w).

mixture. The reaction mixture was refluxed for 2 h. The

{5,15-bis[p-

resulting solid was purified by silica gel column (methoxycarbonyl)phenyl]porphyrinato}platinum(II)

chromatography using a CH₂Cl₂/MeOH (95:5 v/v) mixture as [PtD(CMP)P] was prepared from 40 mg (0.07 mmol) of

eluent to give PdTMesPP as a pink crystalline powder (26 mg, H₂D(CMP)P and 56 mg (0.208 mmol) of PtCl₂dissolved in 12

96%). ¹H NMR (600 MHz, CDCl₃, 25 °C): δ_H1.37 (t, ³J_H,H= 7.0 Hz, mL of benzonitrile. The reaction mixture was stirred under

6H, OCH₂CH₃), 1.85 (s, 12H, o-CH₃), 1.86 (s, 6H, o-CH₃), 2.61 (s, reflux for 4 h. The resulting solid was purified by column

3H, p-CH₃), 2.64 (s, 6H, p-CH₃), 4.19–4.27 (m, 2H, OCH₂CH₃), chromatography on silica gel using CH₂Cl₂as eluent to give

1

4.48–4.57 (m, 2H, OCH₂CH₃), 7.26 (br s, 2H, m-Ph), 7.29 (br s, PtD(CMP)P as an orange crystalline powder (25 mg, 46%). H

4H, m-Ph), 8.56 (d, ³J_H,H= 4.8 Hz, 2H, Hβ), 8.61 (d, ³J_H,H= 4.8 Hz, NMR (600 MHz, CDCl₃, 25 °C): δ_H4.14 (s, 6H, Ph-CH₃), 8.30 (d,

2H, Hβ), 8.76 (d, ³J_H,H= 5.2 Hz, 2H, Hβ), 10.31 (d, ³J_H,H= 5.2 Hz, ³J_H,H= 7.9 Hz, 4H, o-Ph), 8.47 (d, ³J_H,H= 8.0 Hz, 4H, m-Ph), 8.90

2H, Hβ). ³¹P{¹H} 144.21 NMR (600 MHz, CDCl₃, 25 °C): δ_P22.72. (d, ³J_H,H= 4.8 Hz, 4H, Hβ), 9.26 (d, ³J_H,H= 4.8 Hz, 4H, Hβ), 10.21

¹³C{¹H} NMR (150 MHz, CDCl₃, 25 °C): δ_c16.46 (d, ²J_C,_P= 6.6 Hz, (s, 2H, H_meso). MS (MALDI-TOF): m/z = 771.15 ([M]⁺, calcd. for

2C, OCH₂CH₃), 21.46 (1C, p-CH₃), 21.48 (2C, o-CH₃), 21.58 (4C, C₃₆H₂₄N₄O₄Pt m/z = 771.14). HRMS (ESI): m/z = 771.14461

o-CH₃), 21.63 (2C, p-CH₃), 62.71 (d, ²J_C,_P= 4.4 Hz, 2C, OCH₂CH₃), ([M]⁺, calcd. for C₃₆H₂₄N₄O₄Pt m/z = 771.14428). UV–vis [CHCl₃;

2

101.35 (d, J_C,_P= 187.1 Hz, 1C, meso-C), 120.50 (2C, meso-C), λ_max, nm (log ε)]: 393 (5.31), 502 (4.25), 531 (4.14). IR (neat,

122.92 (1C, meso-C), 127.81 (2C, m-C_Mes), 127.85 (4C, m-C_Mes), cm^–1): ν_max2953 (m), 2915 (s), 2849 (m), 1716 (s, C=O), 1604

129.79 (2C, β-C), 131.00 (2C, β-C), 131.47 (2C, β-C), 132,88 (2C, (w), 1541 (w), 1492 (w), 1457 (w), 1428 (w), 1398 (w), 1376

β-C), 137.40 (1C, C_Mes), 137.72 (2C, C_Mes), 137.92 (2C, C_Mes), (w), 1363 (w), 1310 (w), 1222 (w), 1195 (w), 1179 (m), 1096

137.94 (2C, C_Mes), 139.04 (1C, C_Mes), 139.11 (4C, C_Mes), 140.44 (m), 1075 (m), 1047 (w), 1013 (m), 968 (w), 928 (w), 855 (w),

2

(2C, α-C), 140.60 (2C, α-C), 142.18 (2C, α-C), 144.48 (d, J_C,_P= 848 (w), 821 (w), 782 (m), 755 (m), 723 (s), 694 (m), 646 (w),

18.2 Hz, 2C, α-CP). HRMS (ESI): m/z = 904.27887 ([M]⁺, calcd. 615 (w), 594 (w), 569 (w), 554 (w).

for C₅₁H₅₁N₄O₃PPd m/z = 904.27281), 905.28173 ([M+H]⁺,

[10-(Diethoxyphosphoryl)-5,15-bis(p-

= 905.28064), 927.26365 tolyl)porphyrinato]platinum(II) (PtDTolPP) was prepared from

calcd. for C₅₁H₅₂N₄O₃PPd m/z

([M+Na]⁺, calcd. for C₅₁H₅₁N₄O₃PPdNa m/z = 927.26258). UV– 7 mg (0.011 mmol) of H₂DTolPP and 7.5 mg (0.022 mmol) of

vis [toluene; λ_max, nm (log ε)]: 415 (5.38), 527 (4.29), 560 PtCl₂dissolved in 2 mL of benzonitrile. The reaction mixture

(4.28). IR (neat, cm^–1): ν_max2918 (w), 2852 (w), 1729 (w), 1610 was stirred under reflux for 4 h. The resulting solid was

(w), 1561 (w), 1540 (w), 1435 (br, m), 1376 (w), 1348 (w), 1333 purified by column chromatography on silica gel using CHCl₃/n-

(w), 1302 (w), 1252 (m), 1207 (w), 1161 (w), 1088 (w), 1069 hexane (1:1 v/v) as eluent to give PtDTolPP as an orange red

(m), 1044 (m), 1011 (s), 953 (br, m), 884 (m), 865 (w), 851 (m), crystalline powder (7.8 mg, 85%). ¹H NMR (600 MHz,

3

830 (w), 799 (m), 755 (w), 727 (m), 711 (m), 598 (m), 575 (w), CDCl₃/CD₃OD 2:1 v/v, 25 °C): δ_H1.16 (t, J_H,H= 7.0 Hz, 6H,

561 (m), 538 (m).

OCH₂CH₃), 2.53 (s, 6H, Ph-CH₃), 3.98–4.05 (m, 2H, OCH₂CH₃),

3

General Procedure for Platinum(II) Metalation. A solution 4.24–4.30 (m, 2H, OCH₂CH₃), 7.39 (d, J_H,H= 7.6 Hz, 4H, m-Ph),

of the free-base porphyrin H₂R¹P–H₂R⁴P or H₂R¹PP–H₂R⁴PP 7.83 (d, ³J_H,H= 7.7 Hz, 4H, o-Ph), 8.68 (d, ³J_H,H= 4.8 Hz, 2H, Hβ),

3

and PtCl₂(2–10 equiv.) were refluxed in benzonitrile. During 8.74 (d, J_H,H= 5.2 Hz, 2H, Hβ), 8.99 (d, J_H,H= 4.8 Hz, 2H, Hβ),

the heating, the color of the reaction mixture became brown- 9.96 (s, 1H, H_meso), 10.06 (d, ³J_H,H= 5.3 Hz, 2H, Hβ). ³¹P{¹H} NMR

orange. The degree of conversion was monitored by MALDI- (600 MHz, CDCl₃/CD₃OD 2:1 v/v, 25 °C): δ_P22.52. MS (MALDI-

TOF mass-spectrometry and UV–vis spectroscopy. After TOF): m/z = 820.23 ([M+H]⁺, calcd. for C₃₈H₃₄N₄O₃PPt m/z =

complete conversion of the starting porphyrin, the reaction 820.19). HRMS (ESI): m/z = 819.19732 ([M]⁺, calcd. for

mixture was cooled to room temperature and n-hexane was C₃₈H₃₃N₄O₃PPt m/z = 819.19357). UV–vis [toluene; λ_max, nm

added. The resulting precipitate was filtrated, washed two (log ε)]: 396 (5.41), 510 (4.23), 546 (4.42). IR (neat, cm^–1): ν_max

times with n-hexane and dissolved in chloroform. After 2952 (m), 2920 (m), 1609 (w), 1541 (w), 1439 (w), 1391 (w),

evaporation of the solvent, the residue was purified by column 1375 (w), 1363 (w), 1333 (w), 1311 (w), 1246 (m, P=O), 1216

chromatography on silica gel to afford PtR¹P–PtR⁴P or PtR¹PP– (w), 1179 (w), 1162 (w), 1088 (w), 1069 (m), 1042 (w), 1015 (s),

PtR⁴PP.

966 (s), 963 (m), 892 (m), 873 (m), 850 (w), 800 (s), 792 (m),

[5,15-Bis(p-tolyl)porphyrinato]platinum(II) (PtDTolP) was 781 (m), 710 (m), 694 (m), 664 (w), 640 (w), 603 (s), 571 (s),

prepared from 20 mg (0.041 mmol) of H₂DTolP and 33 mg 552 (w).

(0.123 mmol) of PtCl₂dissolved in 7 mL of benzonitrile. The

{10-(Diethoxyphosphoryl)-5,15-bis[p-

reaction mixture was stirred under reflux for 4 h. The resulting (methoxycarbonyl)phenyl]porphyrinato}platinum(II)

solid was purified by column chromatography on silica gel [PtD(CMP)PP] was prepared from 15 mg (0.021 mmol) of

using CH₂Cl₂as eluent to give PtDTolP as an orange crystalline H₂D(CMP)PP and 11.2 mg (0.042) of PtCl₂dissolved in 4 mL of

1

powder (20.6 mg, 72%). H NMR (600 MHz, CDCl₃, 25 °C): δ_Hbenzonitrile. The reaction mixture was stirred under reflux for

3

2.73 (s, 6H, Ph-CH₃), 7.58 (d, J_H,H= 7.6 Hz, 4H, m-Ph), 8.08 (d,

4

h. The resulting solid was purified by column

³J_H,H= 7.8 Hz, 4H, o-Ph), 8.97 (d, ³J_H,H= 4.8 Hz, 4H, Hβ), 9.21 (d, chromatography on silica gel using CHCl₃/n-hexane (1:1 v/v) as

³J_H,H= 4.9 Hz, 4H, Hβ), 10.15 (s, 2H, H_meso). MS (MALDI-TOF): eluent to give PtD(CMP)PP as an red orange crystalline powder

m/z = 684.18 ([M+H]⁺, calcd. for C₃₄H₂₄N₄Pt m/z = 684.17). (12.3 mg, 70%). H NMR (600 MHz, CDCl₃/CD₃OD (2:1 v/v), 25

1

12 | J. Name., 2012, 00, 1-3

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3

°C): δ_H1.15 (t, J_H,H= 7.0 Hz, 6Н, OCH₂CH₃), 3.92 (s, 6Н, 1727 (w), 1698 (w), 1610 (w), 1571 (w), 1542 (w),_V1_ie4_w5_A2_rti(_cb_ler_O, _nm_lin)_e,

PhCOOCH₃), 3.99–4.06 (m, 2Н, OCH₂CH₃), 4.24–4.30 (m, 2Н, 1390 (w), 1375 (w), 1348 (w), 1337 (w), 1311 (m), 1269 (w),

DOI: 10.1039/C9DT01577A

3

OCH₂CH₃), 8.01 (d, J_H,H= 7.9 Hz, 4H, o-Ph), 8.23 (d, J_H,H= 7.9 1243 (w), 1224 (w), 1215 (w), 1187 (w), 1168 (w), 1067 (m),

Hz, 4H, m-Ph), 8.53 (d, ³J_H,H= 4.8 Hz, 2H, Hβ), 8.62 (d, ³J_H,H= 5.3 1015 (s), 953 (w), 908 (w), 865 (w), 845 (m), 836 (s), 795 (s),

3

Hz, 2H, Hβ), 8.95 (d, J_H,H= 4.8 Hz, 2H, Hβ), 9.91 (s, 1H, H_meso), 776 (m), 718 (s), 693 (m), 672 (m), 648 (w), 595 (w).

10.08 (d, J_H,H= 5.3 Hz, 2H, Hβ). ³¹P{¹H} NMR (600 MHz,

[10-(diethoxyphosphoryl)-5,15-

3

CDCl₃/CD₃OD 2:1 v/v, 25 °C): δ_P21.91. MS (MALDI-TOF): m/z = dimesitylporphyrinato]platinum(II) (PtDMesPP) was prepared

908.04 ([M+H]⁺, calcd. for C₄₀H₃₄N₄O₇PPt m/z = 908.17). HRMS from 25 mg (0.037 mmol) of H₂DMesPP and 97 mg (0.366

(ESI): m/z = 907.17703 ([M]⁺, calcd. for C₄₀H₃₃N₄O₇PPt m/z = mmol) of PtCl₂in 6 mL of benzonitrile. The reaction mixture

907.17324). UV–vis [toluene; λ_max, nm (log ε)]: 396 (5.51), 510 was stirred under reflux for 8 h. The resulting solid was

(4.44), 546 (4.61). IR (neat, cm^–1): ν_max2980 (w), 2921 (w), purified by silica gel column chromatography and gel

2849 (w), 1717 (s, C=O), 1607 (m), 1566 (w), 1545 (w), 1433 permeation chromatography using a CH₂Cl₂/MeOH (95:5 v/v)

(m), 1392 (w), 1307 (w), 1274 (s, P=O), 1252 (s, P = O), 1217 mixture and CHCl₃as eluent, respectively, to give PtDMesPP as

(w), 1178 (w), 1162 (w), 1110 (m), 1089 (m), 1074 (w), 1043 a pink crystalline powder (6 mg, 18%). ¹H NMR (600 MHz,

3

(w), 1013 (s), 960 (s), 893 (m), 865 (m), 822 (w), 786 (m), 761 CDCl₃, 25 °C): δ_H1.36 (t, J_H,H= 7.0 Hz, 6H, OCH₂CH₃), 1.85 (s,

(s), 728 (s), 709 (s), 694 (m), 586 (s), 561 (s), 551 (m).

12H, o-CH₃), 2.65 (s, 6H, p-CH₃), 4.20–4.28 (m, 2H, OCH₂CH₃),

(5,15-Dimesitylporphyrinato)platinum(II) (PtDMesP) was 4.49–4.57 (m, 2H, OCH₂CH₃), 7.31 (br s, 4H, m-Ph), 8.71 (d, ³J_H,H

prepared from 21 mg (0.038 mmol) of H₂DMesP and 102 mg = 4.7 Hz, 2H, Hβ), 8.77 (d, ³J_H,H= 5.3 Hz, 2H, Hβ), 9.12 (d, ³J_H,H

=

(0.384 mmol) of PtCl₂in 6 mL of benzonitrile. The reaction 4.7 Hz, 2H, Hβ), 10.06 (s, 1H, H_meso), 10.34 (d, ³J_H,H= 5.1 Hz, 2H,

mixture was stirred under reflux for 18 h. The resulting solid Hβ). ³¹P{¹H} NMR (600 MHz, CDCl₃, 25 °C): δ_P21.98. ¹³C{¹H}

2

was purified by silica gel column chromatography and gel NMR (150 MHz, CDCl₃, 25 °C): δ_c16.46 (d, J_C,_P= 7.2 Hz, 2C,

2

permeation chromatography using CHCl₃as eluent to give OCH₂CH₃), 21.49 (6C, p+o-CH₃), 62.83 (d, J_C,_P= 4.5 Hz, 2C,

PtDMesP as an orange crystalline powder (22 mg, 78%). H OCH₂CH₃), 103.19 (d, ²J_C,_P= 185.7 Hz, 1C, meso-C), 109.93 (2C,

1

NMR (600 MHz, CDCl₃, 25 °C): δ_H1.86 (s, 12H, o-CH₃), 2.66 (s, meso-C), 120.71 (1C, meso-C), 127.95 (4C, m-C_Mes), 129.57 (2C,

3

6H, p-CH₃), 7.32 (br s, 4H, m-Ph), 8.80 (d, J_H,H= 4.8 Hz, 4H, β-C), 131.25 (2C, β-C), 132.23 (2C, β-C), 132.85 (2C, β-C),

Hβ), 9.18 (d, ³J_H,H= 4.8 Hz, 4H, Hβ), 10.11 (s, 2H, H_meso). ¹³C{¹H} 137.22 (2C, C_Mes), 138.07 (2C, C_Mes), 139.07 (4C, C_Mes), 139.68

2

NMR (150 MHz, CDCl₃, 25 °C): δ_c21.49 (4C, o-CH₃), 21.50 (2C, (2C, α-C), 140.20 (2C, α-C), 141.71 (2C, α-C), 143.21 (d, J_C,_P=

p-CH₃), 107.24 (2C, meso-C), 119.48 (2C, meso-C), 127.90 (4C, 17.8 Hz, 2C, α-CP). HRMS (ESI): m/z = 898.24236 ([M+Na]⁺,

m-C_Mes), 129.96 (4C, β-C), 131.35 (4C, β-C), 137.37 (2C, C_Mes), calcd. for C₄₂H₄₁N₄O₃PPtNa m/z = 898.24597). UV–vis [toluene;

137.91 (2C, C_Mes), 139.23 (4C, C_Mes), 140.34 (4C, α-C), 140.42 λ_max, nm (log ε)]: 394 (5.32), 510 (4.12), 545 (4.32). IR (neat,

(4C, α-C). HRMS (ESI): m/z = 739.22774 ([M]⁺, calcd. for cm^–1): ν_max2976 (w), 2919 (w), 2855 (w), 1726 (w), 1610 (w),

C₃₈H₃₂N₄Pt m/z = 739.22723), 762.21649 ([M+Na]⁺, calcd. for 1563 (w), 1543 (w), 1454 (m), 1440 (m), 1390 (w), 1377 (w),

C₃₈H₃₂N₄PtNa m/z = 762.21669). UV–vis [toluene; λ_max, nm (log 1361 (w), 1333 (w), 1301 (w), 1254 (m), 1218 (w), 1165 (w),

ε)]: 391 (5.38), 501 (4.27), 532 (4.19). IR (neat, cm^–1): ν_max2954 1087 (w), 1067 (m), 1044 (m), 1017 (s), 961 (br, m), 884 (m),

(m), 2921 (m), 2852 (m), 1828 (w), 1786 (w), 1736 (w), 1711 856 (m), 837 (w), 800 (m), 736 (w), 725 (w), 712 (w), 696 (w),

(w), 1606 (w), 1589 (w), 1570 (w), 1521 (m), 1447 (br, m), 1398 603 (m), 578 (w), 562 (m), 542 (w).

(w), 1371 (m), 1341 (w), 1324 (w), 1306 (m), 1260 (w), 1242

(w), 1217 (w), 1164 (w), 1144 (w), 1070 (m), 1059 (m), 1041 trimesitylporphyrinato]platinium(II)

(w), 1013 (s), 915 (w), 853 (s), 836 (m), 789 (m), 778 (s), 758 prepared from 10 mg (0.013 mmol) of H₂TMesPP, 33 mg

(m), 720 (s), 698 (s), 672 (w), 646 (w), 567 (w). (0.124 mmol) of PtCl₂and 10 mg (0.122 mmol) NaOAc in 3 mL

[10-(diethoxyphosphoryl)-5,15,20-

(PtTMesPP)

was

(5,15,20-Trimesitylporphyrinato)platinum(II) (PtTMesP) of benzonitrile according to the general procedure. The

was prepared from 10 mg (0.015 mmol) of H₂TMesP and 40 reaction mixture was stirred at 150 °C for 1 h. The resulting

mg (0.150 mmol) of PtCl₂in 3 mL of benzonitrile. The reaction solid was purified by silica gel column chromatography and gel

mixture was stirred under reflux for 50 h. The resulting solid permeation chromatography using CH₂Cl₂/MeOH (95:5 v/v)

was purified by silica gel column chromatography and gel mixture and CHCl₃as eluent, respectively, to give PtTMesPP as

permeation chromatography using CHCl₃as eluent to give pink crystalline powder (11 mg, 89%). ¹H NMR (600 MHz,

3

PtTMesP as an orange-brown crystalline powder (11 mg, 85%). CDCl₃, 25 °C): δ_H1.35 (t, J_H,H= 6.9 Hz, 6H, OCH₂CH₃), 1.87 (s,

¹H NMR (600 MHz, CDCl₃, 25 °C): δ_H1.87 (s, 18H, o-CH₃), 2.62 12H, o-CH₃), 1.88 (s, 6H, o-CH₃), 2.62 (s, 3H, p-CH₃), 2.64 (s, 6H,

(s, 3H, p-CH₃), 2.64 (s, 6H, p-CH₃), 7.27 (br s, 2H, m-Ph), 7.30 p-CH₃), 4.17–4.25 (m, 2H, OCH₂CH₃), 4.47–4.55 (m, 2H,

(br s, 4H, m-Ph), 8.61 (d, ³J_H,H= 4.8 Hz, 2H, Hβ), 8.62 (d, J_H,H

=

OCH₂CH₃), 7.28 (br s, 6H, m-Ph), 8.53 (d, ³J_H,H= 4.8 Hz, 2H, Hβ),

3

4.8 Hz 2H, Hβ), 8.75 (d, J_H,H= 4.8 Hz, 2H, Hβ), 9.14 (d, J_H,H

8.56 (d, J_H,H= 4.8 Hz, 2H, Hβ), 8.71 (d, J_H,H= 5.2 Hz, 2H, Hβ),

3

4.8 Hz, 2H, Hβ), 10.03 (s, 1H, H_meso). ¹³C{¹H} NMR (150 MHz, 10.28 (d, J_H,H= 5.2 Hz, 2H, Hβ). ³¹P{¹H} NMR (600 MHz, CDCl₃,

CDCl₃, 25 °C): δ_c21.48 (1C, p-CH₃), 21.49 (2C, o-CH₃), 21.53 (4C, 25 °C): δ_P22.09. ¹³C{¹H} NMR (150 MHz, CDCl₃, 25 °C): δ_c16.44

o-CH₃), 21.65 (2C, p-CH₃), 106.75 (1C, meso-C), 119.68 (2C, (d, ²J_C,_P= 6.6 Hz, 2C, OCH₂CH₃), 21.46 (1C, p-CH₃), 21.47 (2C, o-

2

meso-C), 120.37 (1C, meso-C), 127.81 (2C, m-C_Mes), 127.86 (4C, CH₃), 21.51 (4C, o-CH₃), 21.56 (2C, p-CH₃), 62.75 (d, J_C,_P= 4.9

m-C_Mes), 129.78 (2C, β-C), 129.93 (2C, β-C), 129.99 (2C, β-C), Hz, 2C, OCH₂CH₃), 102.54 (d, J_C,_P= 185.6 Hz, 1C, meso-C),

2

131.14 (2C, β-C), 137,51 (2C, C_Mes), 137.62 (2C, C_Mes), 137.77 121.01 (2C, meso-C), 123.41 (1C, meso-C), 127.86 (2C, m-C_Mes),

(2C, C_Mes), 137.82 (2C, C_Mes), 139.26 (4C, C_Mes), 140.23 (2C, α- 127.90 (4C, m-C_Mes), 129.38 (2C, β-C), 130.86 (2C, β-C), 131.24

C), 140.28 (2C, α-C), 140.50 (2C, α-C), 140.55 (2C, α-C). HRMS (2C, β-C), 132.59 (2C, β-C), 137.00 (1C, C_Mes), 137.33 (2C, C_Mes),

(ESI): m/z = 857.30273 ([M]⁺, calcd. for C₄₇H₄₂N₄Pt m/z = 137.99 (2C, C_Mes), 139.03 (1C, C_Mes), 139.07 (4C, C_Mes), 139.67

2

857.30555). UV–vis [toluene; λ_max, nm (log ε)]: 397 (5.26), 506 (2C, α-C), 140.01 (2C, α-C), 141.74 (2C, α-C), 143.44 (d, J_C,_P=

(4.25), 536 (3.97). IR (neat, cm^–1): ν_max2916 (w), 2852 (w), 18.5 Hz, 2C, α-CP), signal of one C_Mesis not observed. HRMS

J. Name., 2013, 00, 1-3 | 13

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A spectrum was recorded

(ESI): m/z = 993.33999 ([M]⁺, calcd. for C₅₁H₅₁N₄O₃PPt m/z =

993.33448), 1016.32463 ([M+Na]⁺, calcd. for C₅₁H₅₁N₄O₃PPtNa

m/z = 1016.32387). UV–vis [toluene; λ_max, nm (log ε)]: 402

(5.13), 515 (4.07), 549 (3.97). IR (neat, cm^–1): ν_max2956 (s),

2924 (s), 2857 (m), 1726 (s), 1610 (w), 1579 (w), 1542 (w),

1457 (br, m), 1377 (w), 1354 (w), 1338 (w), 1273 (br, m), 1209

(w), 1162 (w), 1122 (m), 1072 (m), 1041 (m), 1019 (s), 962 (br,

m), 885 (w), 865 (w), 853 (w), 833 (w), 801 (m), 741 (m), 728

(w), 712 (m), 651 (w), 601 (m), 563 (m), 541 (w).

(typically, 5000–7000 min).

View Article Online

systematically before and after irradiat^Dio^On^I.^{: 1}T⁰h^.1e⁰³⁹li^/g^Ch⁹t^DTs⁰o¹u⁵r⁷c^7Ae

was an Osram Powerstat HQI BT 400 W lamp (metal

halogenide lamp with UV filter) emitting in the visible range

(the spectrum of the lamp provided by the manufacturer is

displayed in Figure S79, ESI) and was placed in a fixed position

20 cm away from the glass reactor, both devices being aligned

with respect to their centers. The setup remained untouched

during all experiments to ensure reproducibility, while the

lamp was allowed to warm up and to stabilize for at least half

an hour before starting the experiments. In most cases

however, it remained switched on in between the irradiations.

During filling/emptying operations and before exposing the

porphyrin solution to the light once it was introduced in the

cell, the latter was protected by an UV filtering Plexiglas screen

covered with an aluminum foil.

All solutions of porphyrins were freshly prepared by

carefully weighing a few milligrams of solid with a Mettler-

Toledo XP205 Delta Range balance (resolution: 0.01 mg) into a

5 mL volumetric flask. Compounds were dissolved in analytical

grade DMF (Sigma-Aldrich) dried over molecular sieves or

toluene (Sigma-Aldrich) dried over Al₂O₃and the resulting

solutions were stored in the dark. In few instances, short (less

than 1 min) sonication was required. The reactor was filled

with 50 mL of solvent using a glass pipet and allowed to reach

the equilibrium temperature. After performing the zeroing

operations of the spectrophotometer, an aliquot of the

porphyrin mother solution was injected in the reactor with a

1000 L Eppendorf micropipette; the introduced volume was

calculated so that the final concentration after dilution was 5

M unless otherwise noted. Immediately after, a spectrum

was measured while protecting the cell with the screen. At the

end of the data collection, the cell was exposed to the light

source while starting the recording of the absorbance decay

curve. Data manipulation and nonlinear least-squares fitting to

a monoexponential decay function [y = a exp(–k_obst) + bt + c]

were performed with Origin 8.0 (Figure S83-S85, ESI).

Photophysical measurements

UV−vis absorption spectra were recorded on either a

Helios Alpha spectrophotometer (Thermo Electron) and on a

CARY 50 or a CARY 5000 (Varian), using a rectangular quartz

cell (1−10 mm). Photophysical solution studies were

performed for the dye concentrations ranging between 3 and

7 M. Luminescence spectra were recorded on a FluoroLog® 3

spectrofluorometer (Horiba Scientific) equipped with a NIR-

sensitive R2658 photomultiplier from Hamamatsu (300–1050

nm). All dye solutions were deoxygenated in a screw-cap

cuvette (Hellma) by bubbling high purity nitrogen (99.9999%)

through the solution for at least 15 min. Absolute quantum

yields at room temperature were measured with an

integrating sphere from Horiba. The luminescence decay times

were acquired in the time domain on the FluoroLog® 3

spectrofluorometer equipped with a DeltaHub module (Horiba

Scientific) controlling a SpectraLED-392 (λ = 392 nm) and using

DAS-6 Analysis software for data analysis. For characterization

of the oxygen sensing properties, the composition of the gas

was adjusted with a custom-build gas-mixing device based on

mass-flow controllers from Voegtlin (www.red-y.com) by

mixing compressed air and dinitrogen. The luminescence

spectra and phosphorescence decay times at 77 K were

recorded for the dye solutions in a mixture of toluene and

tetrahydrofuran (4:6 v/v), which produces good glasses at this

temperature. The measurements were made in the Institute of

Analytical Chemistry and Food Chemistry, Graz University of

Technology.

Conflicts of interest

Photostability studies

There are no conflicts to declare.

Photostability measurements were conducted in a 100 mL

double-jacketed glass vessel equipped with a magnetic stirring

bar and fitted to a Lauda RE106 water circulator ensuring a

constant temperature of 25.0(5) °C. The cell was sealed with a

5-necked lid from Metrohm (reference 6.1414.010) fitted with

a thermometer and an immersion probe having a 1 cm optical

path length made of Suprasil 300 (Hellma, reference 6610202).

Acknowledgements

This work was supported by the Russian Foundation for

Basic Research (grant number 18-33-00734-mol-a), the Russian

Academy of Sciences (RAS), and the Centre National de la

Recherche Scientifique (CNRS). It was carried out in the

framework of the International Associated French–Russian

Laboratory of Macrocyclic Systems and Related Materials

(LAMREM) of CNRS and RFBR (RFBR grant number 17-53-

16028). Some measurements were performed using

equipment of CKP FMI IPCE RAS. Prof. Anthony Romieu is

warmly acknowledged for helpful discussions concerning this

work. We are also grateful to Marie-José Penouilh and Quentin

Bonnin for their technical assistance.

The probe was connected to

a

Cary 50 (Varian)

spectrophotometer through fiber guides and a fiber optic

coupler. Prior to each experiment, the reference spectrum was

recorded with the pure solvent and the absorbance set to zero

at the wavelength used to monitor the time course of the

reaction. Visible absorption spectra were recorded over the

350–800 nm range by taking a point at each nanometer at a

scan rate of 400 nm/min. Kinetic traces were recorded at the

maximum of the Soret band with an average time of 0.1 s by

taking one point every minute until the end of the reaction

14 | J. Name., 2012, 00, 1-3

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27

28

29

Y. Y. Enakieva, A. G. Bessmertnykh, Y. G. Gorbunova, C.

View Article Online

Notes and references

Stern, Y. Rousselin, A. Y. Tsivadze an^Dd^OR^I:. ¹G⁰u^.1i⁰la³r⁹d^/,^CO^9Drg^T.⁰L¹e⁵t⁷t⁷.^A,

1

2

3

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Article Doi

Platinum(ii) and palladium(ii) complexes with electron-deficient: Meso -diethoxyphosphorylporphyrins: Synthesis, structure and tuning of photophysical properties by varying peripheral substituents

DOI: 10.1039/c9dt01577a

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