Conformational and structural studies of meso monosubstituted metalloporphyrins - Edge-on molecular interactions of porphyrins in crystals

Article abstract of DOI:10.1016/j.tet.2015.11.008

A series of meso monosubstituted metalloporphyrins were synthesized to assess the structural chemistry of porphyrins with only one substituent. The structures of four nickel(II) and zinc(II) complexes with either alkyl or aryl residues indicate primarily

Full text of DOI:10.1016/j.tet.2015.11.008

Tetrahedron xxx (2015) 1e11
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Tetrahedron
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Conformational and structural studies of meso monosubstituted
metalloporphyrinsdEdge-on molecular interactions of porphyrins
in crystals
,
a
a
b
Mathias O. Senge a , Keith J. Flanagan , Aoife A. Ryan , Claudia Ryppa ,
*
Mandy Donath b, Brendan Twamleya
a School of Chemistry, SFI Tetrapyrrole Laboratory, Trinity Biomedical Sciences Institute, 152-160 Pearse Street, Trinity College Dublin,
The University of Dublin, Dublin 2, Ireland
b
€
€
Institut fur Chemie, Universitat Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Golm, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 27 July 2015
Received in revised form 25 October 2015
Accepted 6 November 2015
Available online xxx
A series of meso monosubstituted metalloporphyrins were synthesized to assess the structural chemistry
of porphyrins with only one substituent. The structures of four nickel(II) and zinc(II) complexes with
either alkyl or aryl residues indicate primarily planar macrocycles. This gives rise to a different type of p-
interactions in the crystal and the formation of dimeric, trimeric or tetrameric porphyrin units that
function as building blocks for the overall crystal structure. Notably, some structures exhibit a unique
edge-on packing of porphyrins, while the molecules of (5-n-butylporphyrinato)nickel(II) forms an un-
usual bilayer type structure where rows of two porphyrin macrocycles are separated by the alkyl residues
arranged in a head-to-head fashion. This adds to the canon of intermolecular porphyrin packing ar-
rangements and is of relevance for the preparation of ordered nanoscopic porphyrin devices.
Ó 2015 Elsevier Ltd. All rights reserved.
Keywords:
Porphyrins
Conformational analysis
Tetrapyrroles
Crystal structure
Crystal packing
1. Introduction
electronic and structural effects of macrocycle substitution. In
terms of physical characterization this has given rise to studies on
Porphyrins are often described as the prime examples of mac-
rocycles capable of coordinating almost any metal in the core. This
and their binding by apoproteins are then taken as a basic rationale
for their biological function at a molecular level. Further fine-
tuning is achieved through the type of central metal and its axial
ligation.1 Additionally, the peripheral substituents modulate the
porphyrin properties through electronic and conformational ef-
fects. Numerous studies have been performed on these conforma-
tional substituent effects, mainly investigated with highly
substituted porphyrins, e.g., dodecasubstituted, nonplanar por-
phyrins, where a large number of residues resulted in steric con-
gestion at the macrocycle periphery with attendant changes in
structural and physicochemical properties.2
the interrelationship of substituents and redox potential and, in
materials chemistry, on the influence of the number and regio-
chemistry of meso substituents on the type and formation of dif-
ferently sized nanospheres and nanorods.9 They also allow the
preparation of more unsymmetrical systems, e.g., the ABCD-type
porphyrins,5,10 and studies on the effect of mixed types of sub-
stitution. While porphyrins with four (6) and two substituents in
a 5,15-pattern (3) constitute materials widely used in porphyrin
chemistry, the mono- (2) and 5,10-disubstituted (4) are only now
beginning to be used in synthetic applications.4,6
With regard to structural chemistry, past studies have compared
the 5,15-A2- and 5,10-A2 regioisomers,8,11 and the influence of in-
dividual bulky meso substituents.12 However, structural data are
still scarce for meso monosubstituted porphyrins. Here we present
the results of X-ray crystallographic studies on 5-substituted met-
alloporphyrins and aim to elucidate some key aspects and general
trends of their structural chemistry identifying a unique type of
intermolecular interactions for porphyrins. We are also presenting
the first crystal structures of 5-substituted Zn(II) porphyrins and
add to existing structures of 5-substituted Ni(II) porphyrin
structures.12a
At the other end of the spectrum are porphyrins with as few
substituents as possible.3 Only recently have advances in synthetic
methodology made an entry in this field possible.4e8 A typical ex-
ample is the so-called Ax-series of porphyrins (1e6, Fig. 1), where
0e4 meso substituents allow
a detailed comparison of the
* Corresponding author. Tel.: þ353 1 896 8537; fax: þ353 1 896 8536; e-mail
address: sengem@tcd.ie (M.O. Senge).
http://dx.doi.org/10.1016/j.tet.2015.11.008
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2
M.O. Senge et al. / Tetrahedron xxx (2015) 1e11
Fig. 2 gives thermal ellipsoid view of the molecular structures of the
porphyrins.
At first glance the structure of Ni(II)2a is that of a standard
ꢀ
porphyrin. The average NieN bond length of 1.951(10) A agrees will
15c
ꢀ
that of the respective A4-porphyrin Ni(II)6a [1.943(1) A].
Fig. 1. The Ax-porphyrin series.
2. Results and discussion
Metal complexes of the A-type free base porphyrins were pre-
pared using standard reaction conditions13,14 and used for crystal-
lization attempts. In addition, a few 5,15-A2 metalloporphyrins
were prepared as well. Within a given series, i.e., 5- or 5,15-
disubstitution, their spectroscopic characteristics follow the
trends observed for the related A4 porphyrins.15 For example, for
the A-series Ni(II)2 the meso arylporphyrins exhibit Soret and long
wavelength absorption bands at w392 and 541 nm, while the
primary and secondary alkylporphyrins show only a negligible shift
of these absorption bands to 394 and 543 nm. However, the tBu
derivative Ni(II)2c has significantly bathochromically shifted ab-
sorption bands at 404 and 567 nm, which is indicative for a dis-
torted macrocycle in solution.12
Despite many attempts over 12 years, only four of the mono-
substituted metalloporphyrins yielded crystals of sufficient quality
for single crystal X-ray crystallographic investigations. The struc-
tures obtained are those of Ni(II)2a, Zn(II)2e, Zn(II)2f, and Ni(II)2h.
Fig. 2. View of the molecular structures of the compounds studied in the crystal.
Thermal ellipsoids show 50% probability. Hydrogen atoms and disordered positions
have been omitted for clarity. Only one of the crystallographically independent mol-
ecules is shown for Zn(II)2f and Ni(II)h.
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M.O. Senge et al. / Tetrahedron xxx (2015) 1e11
3
In line with earlier observations on meso monosubstituted
2,3,7,8,12,13,17,18-octaalkylporphyrins,16 the CaeCmeCa bond angle
for the substituted meso position is smaller [120.6(5)ꢀ] than the one
of the unsubstituted positions (average bond angle¼123.8(5)ꢀ).
Rough structural parameters, such as the average deviation of the
Similarly, the structure of Zn(II)2e exhibits a planar macrocycle
ꢀ
with
D
24¼0.028 A and a smaller CaeCmeCa bond angle for the
substituted meso position (123.8ꢀ vs an average of 126.9ꢀ for the
unsubstituted ones). The zinc center is tetracoordinated with an
ꢀ
average ZneN bond length of 2.047(2) A similar to that of Zn(II)6f
2.043(5) A.18 The molecular packing (Fig. 5) is characterized by the
ꢀ
24 macrocycle atoms from their least-squares plane (D24) show the
porphyrin to be planar and the Cm positions show no evidence for
localized displacements (Table 1). Ni(II)porphyrins which present
less substituted meso-porphyrins often show no core contraction.
Kozlowski et al. suggested that Ni(II)porphyrins occupy a d8 singlet
conformation resulting in eight electrons being doubly occupied
manifold d-orbitals leaving the dx2ꢁy2 empty.17 This results in
a small core size in Ni(II)porphyrins. Both removal, creating of a low
spin, and addition, occupying higher d-orbitals, of an electron re-
sults in an increase in the size of the metal core. As substitutions are
made to the porphyrin macrocycle, electron density can be either
contributed or removed from the ring resulting in changes to the
contractions of the Ni(II) core. There are short contacts between the
formation of standard head-to-tail dimeric aggregates.19 According
to the classification given by Scheidt and Lee1 the dimers are
ꢀ
characterized by a center-to-center (CteCt) distance of 5.114 A,
ꢀ
a mean-plane separation (MPS) of 3.07 A and a slip angle (SA) of
ꢀ
ꢀ
53.1 . This give rise to a lateral shift (LS¼[sin (SA)ꢂCteCt]) of 4.08 A,
which puts this structure into the ‘I’ (intermediate)1 category.
The relatively close mean-plane separation, as defined by the
separation of the two 4N-planes, also gives results in short in-
termolecular contacts. Thus, the two neighboring zinc centers are
ꢀ
separated by only 3.522 A and each zinc center is ‘coordinated’ by
N4 from a neighboring molecule with a separation of 2.95 A. As
ꢀ
shown in Fig. 5 neighboring dimers are orthogonal to each other
ꢀ
pyrrole ring and
range of 2.6e2.8 A are present in the packing of the unit cell.
b
-hydrogen atoms on neighboring units in the
with a close contact of 3.08 A between Zn and H18A. The dimeric
ꢀ
ꢀ
unit shows many close contacts, around 3.35 A, between both
However no interaction with the core seems to be present.
porphyrin rings which stabilize the head-to-tail arrangement in the
Table 1
ꢀ
ꢀ
Selected structural parameters and conformational descriptors for 5-substituted metalloporphyrins [A,
]
Ni(II)2a
Zn(II)2e
Zn(II)2f
Ni(II)2h
Ni(II)2c12a
Cu(II)2c12b
M1
M2
M3
M1
M2
M3
M4
M1
M2
a
Ct-Nav
1.952
2.037
2.035
2.035
2.037
1.954
1.948
1.940
1.955
1.902
1.988
1.985
M-N21
M-N22
M-N23
M-N24
C4eC5eC6
C9eC10eC11
C14eC15eC16
C19eC20eC1
1.942(4)
1.948(5)
1.961(4)
1.958(4)
120.6(5)
123.8(5)
123.1(5)
124.6(6)
0.0402
0.1455
0.044
2.029(2)
2.041(2)
2.036(2)
2.058(2)
123.8(2)
127.3(2)
126.5(3)
126.9(2)
0.1627
0.1948
0.062
2.038(5)
2.039(6)
2.038(6)
2.044(5)
125.0(6)
126.5(6)
126.4(6)
125.8(6)
0.1934
0.1478
0.03
2.035(6)
2.034(5)
2.052(6)
2.031(5)
125.8(6)
125.5(6)
126.6(7)
126.8(6)
0.2035
0.1433
0.004
2.022(5)
2.033(6)
2.041(6)
2.051(6)
125.2(6)
126.5(6)
127.2(6)
126.9(6)
0.1667
0.1441
0.02
1.950(3)
1.961(3)
1.951(3)
1.953(3)
122.3(4)
124.6(4)
124.1(4)
124.0(4)
0.4725
0.1568
0.03
1.946(3)
1.951(3)
1.948(3)
1.948(3)
122.2(4)
124.1(4)
123.2(4)
124.2(4)
0.5341
0.1742
0.03
1.939(3)
1.942(3)
1.935(3)
1.943(3)
121.7(4)
123.7(4)
123.2(4)
123.9(4)
0.9994
0.2404
0.03
1.958(3)
1.953(3)
1.962(3)
1.945(3)
122.0(4)
124.4(4)
122.8(4)
123.6(4)
0.5408
0.1649
0.05
1.906(6)
1.893(6)
1.900(6)
1.905(6)
119.3(7)
123.3(7)
122.4(7)
122.5(7)
2.023
0.572
0.068
0.34
0.88
1.908(3)
1.984(3)
1.988(3)
2.000(3)
119.6(3)
125.7(4)
125.4(4)
126.3(4)
1.16
1.983(3)
1.983(4)
1.988(4)
1.988(3)
119.2(4)
126.5(4)
125.9(4)
126.3(4)
1.1624
0.2061
0.073
b
Doop
c
Dip
0.1939
0.051
0.197
Qd
D
dC5f
24e
0.007
0.028
0.036
0.03
0.05
0.03
0.01
0.13
0.01
0.084
0.15
0.092
0.175
0.093
0.09
0.195
0.63
ꢁ0.01
ꢁ0.06
ꢁ0.07
ꢁ0.2
ꢁ0.38
0.60
dC10f
dC15f
dC20f
ꢁ0.01
0.1
0.02
ꢁ0.11
ꢁ0.18
0.2
0.21
ꢁ0.21
ꢁ0.68
ꢁ0.28
ꢁ0.34
ꢁ0.01
0.1
0.01
0.07
0.06
ꢁ0.10
0.15
ꢁ0.14
ꢁ0.33
0.14
0.63
0.21
0.26
0.02
ꢁ0.04
ꢁ0.13
ꢁ0.18
0.21
0.31
ꢁ0.17
ꢁ0.67
ꢁ0.30
ꢁ0.33
a
Core size.
b
c
d
e
f
Simulated total out-of-plane distortion.
Simulated total in-plane distortion.
Core elongation parameter¼difference in N/N vector lengths: [(N21eN24)þ(N22eN23)]ꢁ[(N21eN22)þ(N23eN24)].
Average deviation from the least-squares plane of the 24-macrocycle atoms.
Displacement of the atom from the 4N-plane.
However, the crystal packing is unlike anything that we have
packing order. Other close contacts present are between b hydro-
ever seen in substituted porphyrins (Fig. 3). Despite the short alkyl
chain, the porphyrin forms parallel running arrays with the alkyl
chains pointing towards each other and two porphyrin macrocycles
forming the other side of the chains; a situation reminiscent of the
gen atoms of one dimer and the nearest molecular unit with
ꢀ
a distance of 2.35e2.84 A. The final close contact is between H55a
ꢀ
and H17a of the nearest molecular unit with a distance of 2.545 A.
Overall, these units of two dimers are arranged in parallel layers
with the porphyrin macrocycle in the middle and the alkyl chains
pointing outwards (not shown).
lipid-bilayer membranes in nature. There is no evidence of
p-in-
teractions or aggregate formation in the crystal. The 4N-planes of
neighboring molecules within a row of porphyrins are tilted against
each other by 64.4ꢀ (Fig. 4). The Cb and Cm hydrogen atoms on one
molecule point towards the edge of a neighboring molecule. In fact,
the packing is rather tight; e.g., the CmeH in one molecule is only
Compound Zn(II)2f formed crystals with three crystallograph-
ically independent porphyrins in the asymmetric unit. The core
geometry about the zinc(II) centers is similar to that of other planar
zinc(II) porphyrins with a tetracoordinated metal center. The av-
ꢀ
ꢀ
separated by 2.97 A from the Cm atom in the next molecule.
erage ZneN bond length of 2.038 A. This is comparable with earlier
The crystals of Ni(II)2e (space group C2/c, a¼50.84, b¼6.49,
work conducted within the group on meso tetrasubstituted por-
¼90.95ꢀ, data not shown due to low resolution) are
phyrin Zn(II) complexes Zn(II)6c (2.014 A) and (5,10,15,20-
ꢀ
ꢀ
c¼11.63 A,
b
15c
ꢀ
isomorphous to that of Ni(II)2a. Thus, exchange of a meso n-butyl
chain for an 1-ethylpropyl residue does not alter the overall mo-
lecular arrangement or the conformational aspects.
tetracyclohexylporphyrinato)zinc(II) (2.029 A).
The three mac-
rocycles are planar, although minor Cm displacements are observed.
Substitution of the 5-position with an aryl residue results in much
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M.O. Senge et al. / Tetrahedron xxx (2015) 1e11
Fig. 3. View of the molecular arrangement in the crystal of Ni(II)2a (down b-axis). Hydrogen atoms have been omitted for clarity. Note, both disordered positions of the n-butyl
residues are shown to illustrate the overall ‘space-filling’ effect.
smaller differences in the CaeCmeCa bond angles compared to the
alkylporphyrins. The porphyrins are arranged in layers with the
meso phenyl groups pointing outwards (not shown). This is the
result of an unusual head-to-tail trimer formation in the crystal.
Fig. 6 illustrates how these units of three porphyrins function as the
building blocks within one of the layers in the crystal.
complexes the bond lengths are marginally smaller in Ni(II)6f
ꢀ
(1.931 A) and (5,10,15,20-tetra(iso-butyl)porphyrinato)nickel(II)
(1.909(3) A).15c The CaeCmeCa bond angles show a similar trend as
ꢀ
observed in the other structures reported here, with the substituted
position exhibiting a smaller angle. However, the difference be-
tween substituted and unsubstituted positions is somewhat
smaller than observed in (5,15-diisopropylporphyrinato)nickel(II)
(119ꢀ for the substituted position and 124ꢀ for the unsubstituted
position).20
The molecular packing of Ni(II)2h is characterized by the for-
mation of rows of porphyrin arrays, which are separated by the
meso substituents (Fig. 7). Chloroform molecules of solvation are
located in the void between the porphyrin rows. The four por-
These trimeric units are held together by relatively strong pep-
interactions. With three zinc centers (ZnB is sandwiched between
Zn and ZnA) present the geometry of these units can be described
ꢀ
as follows: The CteCt distance between Zn and ZnB is 3.67ꢀ9 A, with
ꢀ
a mean-plane separation of 3.139 A and a slip angle of 31.5 . For the
two macrocycles compriꢀsed of ZnB and ZnA the related values are
ꢀ
ꢀ
3.663 A, 3.133 A and 31.2 , respectively. Thus the lateral shifts of the
ꢀ
ꢀ
centers are 1.922 A for Zn . ZnB and 1.898 A for ZnB . ZnA. This
phyrins in the asymmetric unit are grouped in two pairs of p-ag-
puts these
p
-interactions at the upper end of the S (strong) cate-
gregated dimers, which serve as the building blocks of the overall
structure in the crystal (Fig. 8). One dimer (Ni3, Ni4) is of the
standard head-to-tail type and pertaining geometric parameters
gory defined by Scheidt and Lee.1
The structure of the nickel(II) complex of 3,5-di-tert-butylpor-
phyrin Ni(II)2h contains four crystallographically independent
porphyrins in the asymmetric unit. All show minor to significant
ꢀ
ꢀ
ꢀ
are MPS¼3.415 A, CteCt¼4.174 A, SA¼45.1 giving a lateral shift of
ꢀ
the metal centers of 2.95 A. Intriguingly, the other ‘dimer’ (Ni1, Ni2)
degrees of nonplanarity with
0.18 A. The main deviations from planarity involve the Cm positions,
which are alternatively displaced above and below the 4N-plane.
D
24 values ranging from 0.08 to
is of the head-to-head type with both meso residues pointing in the
ꢀ
ꢀ
same direction. Here the two macrocycles are separated by 3.37 A
ꢀ
ꢀ
(MPS), have a CteCt distance of 4.196 A and an SA of 36.5 A,
ꢀ
ꢀ
The Ni-bond length range from 1.94 to 1.96 A, which is similar to
resulting in an LS of 2.496 A. Thus, despite the sterically more un-
those observed in Ni(II)2a. With regards to higher substituted Ni(II)
favorable head-to-head arrangement this aggregate is stronger
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M.O. Senge et al. / Tetrahedron xxx (2015) 1e11
5
Fig. 6. View of the trimeric
p-aggregates formed in the crystal of Zn(II)2f. Hydrogen
atoms have been omitted for clarity.
Fig. 4. Side (top) and top (bottom) view of one of the porphyrin layers in the crystal
structure of Ni(II)2a (down b-axis). Hydrogen atoms and disordered positions have
been omitted for clarity.
Fig. 7. Side (top) and top (bottom) view of one of the porphyrin layers in the crystal
structure of Ni(II)2h (down a-axis). Hydrogen atoms and disordered positions have
been omitted for clarity.
than the head-to-tail one. A number of close intermolecular con-
ꢀ
ꢀ
tacts were observed as well [Ni2eH114 3.135 A, N9eH10 2.609 A,
ꢀ
ꢀ
ꢀ
N13eH10 3.144 A, Ni1eH46 3.055 A, C120eH82 2.767 A, C108eH78
ꢀ
2.715 A].
In comparison the two available structures for metal complexes
of mono-tert-butylporphyrin exhibit more typical
p-stacked ag-
gregates.21 In the nickel(II) derivative Ni(II)2c, with one crystallo-
graphically independent molecule in the asymmetric unit, four
‘dimers’ fill the unit cell with the meso substituents offset by 90ꢀ
against each other.12a The copper(II) derivative Cu(II)2c exhibits the
Fig. 5. View of the
p-aggregates formed in the crystal of Zn(II)2e. Hydrogen atoms
have been omitted for clarity.
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M.O. Senge et al. / Tetrahedron xxx (2015) 1e11
All structures determined here exhibit a significant number of
short non-bonding interactions and close contacts within the in-
dividual packing arrangements. E.g., compound Ni(II)2a presents
with the majority of its short contacts being interactions between
the
b-hydrogen atoms and the pyrrole rings at a distance of
ꢀ
2.89e2.29 A. Zn(II)2e exhibits similar contacts with separations of
2.84e2.64 A, Zn(II)2f shows contact distances of 2.88e2.66 A and
ꢀ
ꢀ
in Ni(II)2h there are interactions with a pyrrole ring of a neigh-
ꢀ
boring macrocycle of 2.7e2.8 A.
b-Hydrogen atoms can also be seen
to interact with solvent chloroform molecules in Ni(II)2h with
ꢀ
contacts distances of 2.94e2.87 A. The 5-meso substituted unit also
participates in short contacts within the crystal structure. For ex-
ample, in Ni(II)2a close contacts between the butyl substituents in
ꢀ
neighboring molecules are in the order of w2.7 A.
A rough inspection of the macrocycle structures using dis-
placement parameters (Table 1) indicates that most of the 5-R-
metalloporphyrins have a planar macrocycle. Only when the ste-
rically highly demanding tert-butyl group is introduced do large
deviations from planarity occur.12 However, the presence of mul-
tiple porphyrins within some asymmetric units and the different
packing arrangements prompted us to analyze the macrocycle
conformations in more detail. This can only be done by the normal-
structural decomposition which allows an identification and com-
parative analysis of individual distortions modes.22 Fig. 9 details the
results for an analysis of all available M2 structures.
Fig. 8. View of the four molecules of Ni(II)2h in the asymmetric unit. Hydrogen atoms
and disordered positions have been omitted for clarity.
standard head-to-tail formation of I-type aggregates.12b Here, the
asymmetric unit contains two crystallographically independent
molecules, which form
form -aggregates of I-type. Thus, here four porphyrin units form
the main building blocks in the crystal.
p-aggregates, which in turn themselves
p
Fig. 9. Normal-coordinate structural decomposition analysis of 5-substituted metalloporphyrins (minimal basis).
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M.O. Senge et al. / Tetrahedron xxx (2015) 1e11
7
For the out-of-plane distortions significant contributions are
observed for the ruf (B1u) and sad (B2u) distortions modes, with
minor contributions from doming (A2u) and wave (Eg) distortions.
No measurable contribution for propellering (A1u) was observed in
any compound. In terms of in-plane distortions a similar picture
emerges. Here, strong A1g (breathing), medium B2g (meso-str), mi-
nor N-str (B1g) and noticeable Eu (pyr-translations), albeit no pyr-
rotation (A2g), were found. Clearly the substituent pattern, i.e., A-
type (2), gives rise to a unique mix of distortion modes. Overall,
significant in-plane distortions are present, although not strong
enough to give rise to a significant core-elongation. As expected the
tert-butyl derivatives exhibit the largest contributions from each
individual distortion mode, an indication of the steric strain im-
posed by the bulky residue. Still, Ni(II)2h exhibits a considerable
contribution from ruf distortion, too, larger than the other sterically
unhindered derivatives. However, overall the two Ni(II)porphyrin
structures reported here show core-geometries similar to triclinic
The assignment of the signals was confirmed by 2D spectra (COSY,
HMBC, HMQC) except for those porphyrins with low solubility.
Electronic absorption spectra were recorded with a Specord S10
instrument (Zeiss) using CH2Cl2 as solvent. Mass spectra were
recorded using a Varian MAT 711 or MAT 112 S mass spectrometer
using the EI technique with direct insertion probe and excitation
energy of 80 eV. FAB spectra were recorded with CH-5 DF in-
strument from Varian.
4.2. Starting materials
The free base porphyrins 2ceg, 3b and 3dee were prepared as
described previously by Ryppa et al.4 The free base porphyrin 3f
was prepared as previously described by Song et al.14 and the free
base 2h as described by Senge et al.10
(2,3,7,8,12,13,17,18-octaethylporphyrinato)nickel(II)
and
(5,10,15,20-tetramethylporphyrinato)nickel(II), which are planar.23
Significant ruffling becomes apparent only with secondary alkyl
substituents, e.g., as indicated by the shorter average NieN bond
4.3. Metallation reactions
4.3.1. Nickel(II) and Copper(II) insertion.13a The free base porphyrin
(1 equiv) was dissolved in DMF (50 mL) and heated to reflux with
the appropriate metal(II) acetate (ca. 10 equiv). The reaction was
monitored by TLC control and the solvent removed under reduced
pressure. The residue was dissolved in CH2Cl2 and the mixture fil-
tered through silica gel, eluting with CH2Cl2. Finally, the solvent
was removed under reduced pressure and the product dried in high
vacuum.
15c
ꢀ
length of 1.907(7) A in Ni(II)4b.
3. Conclusions
In conclusion, four new meso monosubstituted metal-
loporphyrins structures were investigated with X-ray diffraction.
Typically substituted metalloporphyrins form head-to-tail type
p-
aggregates.1,19 Without meso substituents these aggregates can be
quite strong and, as shown, can present a unique packing ar-
rangement depending on the substituents involved. Within the
four structures presented the ‘blocking’ of one side of the tetra-
pyrrole ring leaves three sides to participate in tighter packing ar-
rangements (e.g., Zn(II)2e, Zn(II)2f and Ni(II)2h) or novel crystal
packing motives as seen in Ni(II)2a. We have also shown the first
two examples of crystals structures of 5-substituted Zn(II) por-
phyrins (Zn(II)2e and Zn(II)2f) and added two new structure of 5-
substituted Ni(II) porphyrins (Ni(II)2h and Ni(II)2a) to the only
previously known structure Ni(II)2c.
4.3.2. Zinc(II) insertion.13 The free base porphyrin (1 equiv) and
zinc(II) oxide (2e3 equiv) or zinc(II) acetate (1.5 equiv) was dis-
solved in CH2Cl2 (50 mL) and treated with 3e5 drops of TFA. After
stirring for 10 min the color of the reaction mixture changed from
green to purple-red. The reaction was monitored by TLC control.
The mixture was filtered through silica gel, eluting with CH2Cl2,
followed by removal of the solvent reduced pressure. The product
was dried in high vacuum.
The crystal packing motifs described here expand the list of
known porphyrin aggregate structures, for example, those based on
p
4.4. Metalloporphyrins
-stacking.19 The clear dependence on central metal and sub-
4.4.1. {5-(tert-Butyl)porphyrinato}nickel(II) (Ni(II)2c). The free base
porphyrin H22c (50 mg, 0.14 mmol) was reacted with nickel(II)
acetate and the crude product purified via column chromatography
on silica gel (CH2Cl2: n-hexane¼1: 1, v/v) followed by re-
crystallization from CH2Cl2/MeOH. Yield: 57 mg (0.13 mmol, 98%) of
purple crystals. Mp: >300 ꢀC; Rf¼0.75 (CH2Cl2: n-hexane¼2: 1, v/v,
stituents in the crystal structures is an indication for the variety of
possible molecular arrangements which in less ordered materials.
This may relate to the observation of differently sized and struc-
tured nanomaterials of porphyrins with different numbers of meso
residues,9b,c the different types of structures observed for the in-
teraction of porphyrins with
p
-conjugated surfaces26 or electro-
silica gel, 6ꢂ3 cm); 1H NMR (270 MHz, CDCl3):
d
¼9.64 (AB,
optical devices thereof.27
3JHeH¼5.1 Hz, 2H, Hb), 9.59 (s, 1H, Hmeso), 9.47 (s, 2H, Hmeso), 9.10
3
3
(AB, JHeH¼4.4 Hz, 2H, Hb), 9.04 (AB, JHeH¼4.4 Hz, 2H, Hb), 8.97
3
4. Experimental
(AB, JHeH¼5.1 Hz, 2H, Hb), 2.14 ppm (s, 9H, CH3); 13C NMR
(126 MHz, CDCl3):
131.83, 131.60, 122.91, 103.11, 102.98, 39.12, 38.76 ppm; UV/vis
d
¼141.64, 141.35, 141.17, 138.86, 133.04, 132.42,
4.1. General information
(CH2Cl2): lmax (lg
)¼404 (5.20), 530 (3.96), 567 nm (3.77); MS (EI,
General conditions and instrumentation were as described be-
fore.10 All chemicals used were of analytical grade and purified
before use. Dichloromethane was dried over phosphorous pent-
oxide followed by distillation; THF was dried over sodium followed
by distillation. Silica gel 60 (Merck) was used for column chroma-
tography. Analytical thin-layer chromatography (TLC) was carried
out using silica gel 60 plates (fluorescence indicator F254; Merck).
Melting points are uncorrected and were measured with a Reichert
Thermovar instrument. 1H NMR spectra were recorded at fre-
quencies of 250 (Bruker AM 270 instrument), 270 MHz (Bruker AM
270 instrument) or 500 MHz (Bruker AMX 500). Chemical shifts are
given in ppm and referenced to the TMS signal as internal standard.
4.4.2. {5(-tert-Butyl)porphyrinato}copper(II) (Cu(II)2c). The free
base porphyrin H22c (58 mg, 0.16 mmol) was reacted with cop-
per(II) acetate according to the standard procedure followed by
recrystallization from CH2Cl2/MeOH. Yield: 49 mg (0.11 mmol, 72%)
of purple crystals. Mp: 274 ꢀC; Rf¼0.73 (CH2Cl2: n-hexane¼2: 1, v/v,
silica gel, 6ꢂ3 cm); UV/vis (CH2Cl2): lmax (lg )¼404 (5.44), 534
3
(4.00), 575 nm (3.65); MS (EI, 220 ꢀC, 70 eV): m/z¼427 (89%, [M]ꢃþ),
412 (100%, [MeCH3]þ), 397 (18%, [MeC2H6]ꢃþ), 371 (69%,
Please cite this article in press as: Senge, M. O.; et al., Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2015.11.008

8
M.O. Senge et al. / Tetrahedron xxx (2015) 1e11
[C20H12N4Cu]ꢃþ), 214 (6%, [M]2þ); HRMS (EI): m/z calcd for
[C24H20N4Cu] 427.0984; found 427.0977.
nickel(II) acetate and the crude product purified via column chro-
matography on silica gel (CH2Cl2: n-hexane¼2: 1, v/v) followed by
recrystallization from CH2Cl2/MeOH. Yield: 16 mg (0.04 mmol, 93%)
of purple crystals. Mp: 279e280 ꢀC; Rf¼0.69 (CH2Cl2: n-hexane¼2:
4.4.3. {5-(tert-Butyl)porphyrinato}zinc(II) (Zn(II)2c). The free base
porphyrin H22c (55 mg, 0.15 mmol) was reacted with zinc(II) oxide
according to the standard procedure followed by recrystallization
from CH2Cl2/MeOH. Yield: 31 mg (0.07 mmol, 47%) of purple
crystals. Mp: 279 ꢀC; Rf¼0.41 (CH2Cl2: n-hexane¼2: 1, v/v, silica gel,
1, v/v, silica gel, 6ꢂ3 cm); 1H NMR (500 MHz, CDCl3):
¼9.79 (s, 2H,
d
Hmeso), 9.78 (s, 1H, Hmeso), 9.64 (AB, 3JHeH¼4.8 Hz, 2H, Hb), 9.21 (AB,
3JHeH¼4.8 Hz, 2H, Hb), 9.19 (br s, 4H, Hb), 4.72e4.67 (m, 1H, ethyl-
propyl-CH), 2.81e2.70 (m, 4H, CH2), 0.89 ppm (t, 3JHeH¼7.4 Hz, 6H,
6ꢂ3 cm); 1H NMR (270 MHz, CDCl3):
d
¼9.77 (AB, 3JHeH¼4.7 Hz, 2H,
CH3); 13C NMR (126 MHz, CDCl3):
132.06, 130.58, 130.40, 121.25, 103.82, 102.95, 49.71, 33.89,
d
¼142.72, 141.78, 132.36, 132.22,
3
Hb), 9.58 (s, 1H, Hmeso), 9.55 (s, 2H, Hmeso), 9.01 (AB, JHeH¼4.4 Hz,
2H, Hb), 8.97 (AB, 3JHeH¼4.4 Hz, 2H, Hb), 8.87 (AB, 3JHeH¼4.7 Hz, 2H,
14.01 ppm; UV/vis (CH2Cl2): lmax (lg
)¼396 (5.36), 512 (4.14),
Hb), 2.51 ppm (s, 9H, CH3); 13C NMR (75 MHz, CDCl3):
d¼149.62,
148.69, 148.33, 146.49, 131.46, 131.23, 130.86, 129.68, 127.93, 104.75,
104.09, 41.42, 41.05 ppm; UV/vis (CH2Cl2): lmax (lg
495 (3.88), 540 (4.02), 583 nm (3.59); MS (EI, 70 eV): m/z¼428 (69%,
[M]ꢃþ), 413 (75%, [MeCH3]þ), 388 (100%, [MeC3H4]þ), 372 (96%,
[C20H12N4Zn]ꢃþ); HRMS (EI): m/z calcd for [C24H20N4Zn] 428.0979;
found 428.0983.
3
4.4.8. {5-(1-Ethylpropyl)porphyrinato}copper(II)
(Cu(II)2e). The
free base porphyrin H22e (50 mg, 0.13 mmol) was reacted with
copper(II) acetate according to the standard procedure followed by
chromatography on silica gel (CH2Cl2: n-hexane¼1: 1, v/v) and re-
crystallization from CH2Cl2/hexane: 51 mg (0.11 mmol, 88%) of
purple crystals. Mp: 312 ꢀC; Rf¼0.85 (CH2Cl2: n-hexane¼2: 1, v/v,
4.4.4. (5-Hexylporphyrinato}nickel(II) (Ni(II)2d). The free base
porphyrin H22d (42 mg, 0.11 mmol) was reacted with nickel(II)
acetate and the crude product purified via column chromatography
on silica gel (CH2Cl2: n-hexane¼1: 1, v/v) followed by re-
crystallization from CH2Cl2/MeOH. Yield: 42 mg (0.09 mmol, 87%)
of purple crystals. Mp: >300 ꢀC; Rf¼0.68 (CH2Cl2: n-hexane¼1: 1, v/
silica gel, 6ꢂ3 cm); UV/vis (CH2Cl2): lmax (lg )¼397 (5.68), 522
3
(4.10), 557 nm (3.65); MS (EI, 220 ꢀC, 70 eV): m/z¼441 (100%,
[M]ꢃþ), 412 (94%, [MeC2H5]þ), 397 (26%, [MeC3H8]ꢃþ), 371 (21%,
[MeC5H10]þ), 221 (7%, [M]2þ), 206 (16%, [MeC2H5]2þ); HRMS (EI):
m/z calcd for [C25H22N4Cu] 441.1140; found 441.1149.
v, silica gel, 6ꢂ3 cm); 1H NMR (300 MHz, CDCl3):
¼9.82 (s, 2H,
d
Hmeso), 9.81 (s, 1H, Hmeso), 9.49 (AB, 3JHeH¼4.7 Hz, 2H, Hb), 9.20e9.19
(m, 6H, Hb), 4.72 (t, 2H, 3JHeH¼8.1 Hz, CH2), 2.44e2.38 (m, 2H, CH2),
1.73e168 (m, 2H, CH2), 1.44e135 (m, 4H, CH2), 0.92 ppm (t, 3H,
4.4.9. {5-(1-Ethylpropyl)porphyrinato}zinc(II) (Zn(II)2e). The free
base porphyrin H22e (59 mg, 0.15 mmol) was reacted with zinc(II)
oxide according to the standard procedure followed by column
chromatography an silica (CH2Cl2: n-hexane¼1: 1, v/v) and re-
crystallization from CH2Cl2/hexane. Yield: 46 mg (0.10 mmol, 68%)
of purple crystals. Mp: 325 ꢀC (dec); Rf¼0.64 (CH2Cl2: n-hexane¼2:
3JHeH¼7.2 Hz, CH3); 13C NMR (75 MHz, CDCl3):
¼143.00, 142.16,
d
142.10, 142.06, 132.25, 132.15, 129.37, 118.57, 104.14, 103.21, 37.92,
34.63, 31.84, 30.23, 22.71, 14.12 ppm; UV/vis (CH2Cl2): lmax (lg
)¼
(4%, [MeC5H11
]
2þ); HRMS (EI): m/z calcd for [C26H24N4Ni]
1, v/v, silica gel, 6ꢂ3 cm); 1H NMR (500 MHz,CDCl3):
¼10.18 (s, 2H,
d
450.1354; found 450.1340.
Hmeso), 10.02 (s, 1H, Hmeso), 9.95 (AB, 3JHeH¼4.4 Hz, 2H, Hb), 9.49 (AB,
3JHeH¼4.4 Hz, 2H, Hb), 9.37e9.34 (m, 4H, Hb), 5.31e5.25 (m, 1H,
ethylpropyl-CH), 2.81e2.70 (m, 4H, CH2), 0.89 ppm (t, 3JHeH¼7.4 Hz,
4.4.5. (5-Hexylporphyrinato}copper(II) (Cu(II)2d). The free base
porphyrin H22d (42 mg, 0.11 mmol) was reacted with copper(II)
acetate according to the standard procedure followed by re-
crystallization from CH2Cl2/MeOH. Yield: 40 mg (0.09 mmol, 82%)
of purple crystals. Mp: 269 ꢀC; Rf¼0.70 (CH2Cl2: n-hexane¼1: 1, v/v,
6H, CH3); 13C NMR (126 MHz, CDCl3):
104.89, 103.89, 50.72, 35.07, 14.38 ppm; UV/vis (CH2Cl2): lmax (lg
d
¼149, 131, 124.42, 105.19,
3
(60%, [M]ꢃþ), 413 (100%, [MeC2H5]þ), 398 (46%, [MeC3H8]ꢃþ), 372
(28%, [MeC5H10þH]ꢃþ), 207 (5%, [MeC2H5]2þ), 199 (9%,
[MeC3H8]2þ), 186 (2%, [MeC5H10þH]2þ); HRMS (EI): m/z calcd for
[C25H22N4Zn] 442.1136; found 442.1118.
silica gel, 6ꢂ3 cm); UV/vis (CH2Cl2): lmax (lg )¼398 (6.22), 522
3
(4.10), 557 nm (3.62); MS (EI, 220 ꢀC, 70 eV): m/z¼455 (51%, [M]ꢃþ),
384 (100%, [MeC5H11]þ), 192 (12%, [MeC5H11 2þ); HRMS (EI): m/z
]
calcd for [C26H24N4Cu] 455.1297; found 455.1303.
4.4.10. (5-Phenylporphyrinato}nickel(II) (Ni(II)2f). The free base
porphyrin H22f (50 mg, 0.11 mmol) was reacted with nickel(II)
acetate following the general procedure. Purification involved re-
crystallization from CH2Cl2/MeOH. Yield: 21 mg (0.05 mmol, 37%)
of purple crystals. Mp: >310 ꢀC; Rf 0.65 (CH2Cl2: n-hexane¼2: 1, v/v,
4.4.6. (5-Hexylporphyrinato}zinc(II) (Zn(II)2d). The free base por-
phyrin H22d (39 mg, 0.10 mmol) was reacted with zinc(II) oxide
according to the standard procedure followed by column chroma-
tography an silica (CH2Cl2: n-hexane¼2: 1, v/v) and re-
crystallization from CH2Cl2/hexane. Yield: 25 mg (0.05 mmol, 55%)
of purple crystals. Mp: 259 ꢀC (dec); Rf¼0.47 (CH2Cl2: n-hexane¼1:
silica gel, 6ꢂ3 cm); 1H NMR (300 MHz, CDCl3):
¼10.00 (s, 2H,
d
Hmeso), 9.99 (s, 1H, Hmeso), 9.30 (br s, 4H, Hb), 9.21 (AB, 3JHeH¼4.7 Hz,
3
1, v/v, silica gel, 6ꢂ3 cm); 1H NMR (300 MHz, CDCl3):
d
¼10.02 (s, 2H,
2H, Hb), 8.95 (AB, JHeH¼4.7 Hz, 2H, Hb), 8.10e8.04 (m, 2H, Ph-H),
Hmeso), 9.99 (s,1H, Hmeso), 9.58 (AB, 3JHeH¼4.7 Hz, 2H, Hb), 9.38e9.30
(m, 6H, Hb), 4.97 (t, 3JHeH¼8.1 Hz, 2H, CH2), 2.56e2.53 (m, 2H, CH2),
1.86e1.82 (m, 2H, CH2), 1.49e1.44 (m, 4H, CH2), 0.95 ppm (t,
7.76e7.68 ppm (m, 3H, Ph-H). 13C NMR (75 MHz, CDCl3):
133.89, 132.41, 132.37, 131.94, 127.75, 126.81, 104.75, 103.94 ppm;
d
¼142.64,
UV/vis (CH2Cl2): lmax (lg
)¼392 (5.29), 509 (4.17), 541 nm (4.09);
3JHeH¼7.3 Hz, 3H, CH3); 13C NMR (75 MHz, CDCl3):
d
¼149.42,
148.61, 131.95, 131.77, 131.66, 129.20, 120.81, 104.93, 38.44, 35.64,
31.96, 30.42, 22.79, 14.17 ppm; UV/vis (CH2Cl2): lmax (lg
)¼405
4.4.11. (5-Phenylporphyrinato}copper(II) (Cu(II)2f). The free base
porphyrin H22f (50 mg, 0.11 mmol) was reacted with copper(II)
acetate following the general procedure. Purification involved re-
crystallization from CH2Cl2/MeOH. Yield: 37 mg (0.08 mmol, 64%)
of purple crystals. Mp: >310 ꢀC; Rf¼0.68 (CH2Cl2: n-hexane¼2: 1, v/
(100%, [MeC5H11]þ), 192 (5%, [MeC5H11 2þ); HRMS (EI): m/z calcd
]
for [C26H24N4Zn] 456.1292; found 456.1279.
4.4.7. {5-(1-Ethylpropyl)porphyrinato}nickel(II) (Ni(II)2e). The free
base porphyrin H22e (16 mg, 0.04 mmol) was reacted with
v, silica gel, 6ꢂ3 cm); UV/vis (CH2Cl2): lmax (lg )¼397 (5.50), 521
3
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M.O. Senge et al. / Tetrahedron xxx (2015) 1e11
9
(4.11), 555 nm (3.79); MS (EI, 220 ꢀC, 80 eV): m/z¼447 (100%,
[M]ꢃþ), 224 (8%, [M]2þ); HRMS (EI): m/z calcd for [C26H16N4Cu]
447.0671; found 447.0637.
removed in vacuo. The crude residue was redissolved in CH2Cl2 and
filtered through a short plug of silica gel using CH2Cl2 as eluent. The
solvent was removed in vacuo and the residue was recrystallized
from CH2Cl2/MeOH. Yield: 282 mg (0.507 mmol, 84%) of purple-red
crystals. Rf (CH2Cl2: hexane¼1:1, v/v): 0.76; 1H NMR (400 MHz,
4.4.12. (5-Phenylporphyrinato}zinc(II) (Zn(II)2f). The free base
porphyrin H22f (48 mg, 0.12 mmol) was reacted with zinc oxide
acetate following the general procedure. Purification involved re-
crystallization from CH2Cl2/MeOH. Yield: 22 mg (0.05 mmol, 39%)
of purple crystals. Mp: >310 ꢀC; Rf¼0.51 (CH2Cl2: n-hexane¼2: 1, v/
CDCl3þpyridine-D5¼20:1, v/v): ¼9.98 ppm (s, 2H, Hmeso), 9.95 (s,
d
1H, Hmeso), 9.28 (br s, 4H, Hb), 9.20 (d, J¼4.7 Hz, 2H, Hb), 9.00 (d,
J¼4.7 Hz, 2H, Hb), 7.94 (d, J¼1.8 Hz, 2H, aryl-H), 7.77 (t, J¼1.8 Hz, 1H,
aryl-H), 1.51 (s, 18H, t-butyl-H); 13C NMR (100 MHz, CDCl3):
35.0, 103.7, 104.6, 120.2, 121.1, 129.0, 131.8, 132.2, 132.3, 132.7, 140.1,
142.5, 142.6, 142.8, 142.9, 148.9 ppm; UV/vis (CH2Cl2): lmax (log
394 (5.25), 510 (4.10), 544 nm (3.98); HRMS (MALDI): m/
z¼554.1980 calcd for C34H32N4Ni; found 554.2001.
d
¼31.7,
v, silica gel, 6ꢂ3 cm); 1H NMR (300 MHz, CDCl3):
d
¼10.35e10.31
(m, 3H, Hmeso), 9.55e9.16 (m, 8H, Hb), 8.26e8.23 (m, 2H, Ph-H),
3
7.80e7.77 ppm (m, 3H, Ph-H); UV/vis (CH2Cl2): lmax (lg
)¼402
4.4.17. {5,15-Di(iso-butyl)porphyrinato}copper(II)
(Cu(II)3b). The
free base porphyrin H23b (60 mg, 0.14 mmol) was dissolved in
dichloromethane (60 mL) and mixed with methanol (30 mL), water
(3 drops) and copper acetate (79.2 mg, 0.44 mmol). The mixture
was stirred at rt for 12 h followed by filtration through silica gel
(CH2Cl2). Column chromatography on silica gel (CH2Cl2: n-
hexane¼1:2, v/v) gave a single product fraction, which yielded red
crystals after recrystallization from CH2Cl2/MeOH. Yield: 36 mg
(0.07 mmol, 52%). Mp: >300 ꢀC; Rf¼0.38 (CH2Cl2: n-hexane¼1: 2, v/
4.4.13. {5-(4-Methoxyphenyl)porphyrinato}nickel(II) (Ni(II)2g). The
free base porphyrin H22g (105 mg, 0.25 mmol) was reacted with
nickel(II) acetate following the general procedure. Purification in-
volved recrystallization from CH2Cl2/MeOH. Yield: 98 mg
(0.21 mmol, 82%) of purple crystals. Mp: 321 ꢀC; Rf¼0.61 (CH2Cl2: n-
hexane¼2: 1, v/v, silica gel, 6ꢂ3 cm); 1H NMR (500 MHz, CDCl3):
d
¼9.98 (s, 2H, Hmeso), 9.96 (s, 1H, Hmeso), 9.32e9.27 (m, 4H, Hb), 9.20
3
3
(AB, JHeH¼4.8 Hz, 2H, Hb), 8.98 (AB, JHeH¼4.8 Hz, 2H, Hb),
v, silica gel); UV/vis (CH2Cl2): lmax (lg
3
8.00e7.95 (m, 2H, Ph-H), 7.28e7.22 (m, 2H, Ph-H), 4.07 ppm (s, 3H,
564 nm (3.11); MS (EI, 70 eV): m/z¼438 (8%, [M]þ), 440 (24%,
[MeC3H7]þ), 397 (20%, MeC6H14]þ), 243 (3%, [M]2þ); HRMS (EI): m/
z calcd for [C28H28CuN4] 483.1609; found 483.1592.
CH3); 13C NMR (126 MHz, CDCl3):
134.88, 133.54, 132.39, 132.37, 132.36, 118.58, 112.35, 104.69, 103.83,
d
¼159.43, 143.01, 142.69, 142.55,
55.58 ppm; UV/vis (CH2Cl2): lmax (lg
)¼394 (5.35), 510 (4.15),
4.4.18. (5,15-Dihexylporphyrinato)nickel(II) (Ni(II)3d). The free base
porphyrin H23d (35 mg, 0.07 mmol) was reacted with nickel(II)
acetate and the crude product purified via column chromatography
on silica gel (ethyl acetate: n-hexane¼1: 4, v/v) followed by re-
crystallization from CH2Cl2/MeOH. Yield: 23 mg (0.04 mmol, 59%)
of purple crystals. Mp: 215 ꢀC; Rf¼0.93 (CH2Cl2: n-hexane¼2: 1, v/v,
4.4.14. {5-(4-Methoxyphenyl)porphyrinato}copper(II) (Cu(II)2g). The
free base porphyrin H22g (47 mg, 0.11 mmol) was reacted with
copper(II) acetate following the general procedure. Purification in-
volved silica gel column chromatography on silica gel (eluent:
CH2Cl2: n-hexane¼1: 1, v/v) and recrystallization from CH2Cl2/
MeOH. Yield: 44 mg (0.09 mmol, 82%) of purple crystals. Mp:
>330 ꢀC; Rf¼0.91 (CH2Cl2: n-hexane¼2: 1, v/v, silica gel, 6ꢂ3 cm);
silica gel, 6ꢂ3 cm); 1H NMR (400 MHz, CDCl3):
¼9.74 (s, 2H, Hmeso),
d
9.47 (AB, 3JHeH¼4.7 Hz, 4H, Hb), 9.20 (AB, 3JHeH¼4.7 Hz, 4H, Hb), 4.69
(t, 3JHeH¼8.1 Hz, 4H, CH2), 2.41e2.35 (m, 4H, CH2), 1.72e1.65 (m, 4H,
3
CH2), 1.51e1.34 (m, 8H, CH2), 0.92 ppm (t, JHeH¼7.2 Hz, 6H, CH3);
13C NMR (75 MHz, CDCl3):
d
¼142.53, 141.38, 132.06, 129.31, 117.26,
103.83, 37.06, 34.21, 31.81, 30.14, 22.70, 14.12 ppm; UV/vis (CH2Cl2):
UV/vis (CH2Cl2): lmax (lg
3
lmax (lg
)¼402 (5.37), 518 (4.12), 549 nm (3.63); MS (EI, 220 ꢀC,
MS (EI, 210 ꢀC, 70 eV) m/z: 477 (100%, [M]ꢃþ), 239 (14%, [M]2þ);
HRMS (EI): m/z calcd for [C27H19N4OCu] 478.0855; found 478.0885.
[Me2C5H11]
ꢃþ), 267 (2%, [M]2þ); HRMS (EI): m/z calcd for
[C32H36N4Ni] 534.2293; found 534.2271.
4.4.15. {5-(4-Methoxyphenyl)porphyrinato}zinc(II) (Zn(II)2g). The
free base porphyrin H22g (105 mg, 0.25 mmol) was reacted with
zinc oxide following the general procedure. Purification involved
column chromatography on silica gel (eluent: ethyl acetate: n-
hexane¼1: 4, v/v) and recrystallization from CH2Cl2/MeOH. Yield:
48 mg (0.10 mmol, 95%) of purple crystals. Mp: >330 ꢀC; Rf¼0.36
(CH2Cl2: n-hexane¼2: 1, v/v, silica gel, 6ꢂ3 cm); 1H NMR (300 MHz,
4.4.19. (5,15-Dihexylporphyrinato)copper(II) (Cu(II)3d). The free
base porphyrin H23d (44 mg, 0.09 mmol) was reacted with
copper(II) acetate and the crude product purified via column
chromatography on silica gel (ethyl acetate: n-hexane¼1: 4, v/v)
followed by recrystallization from CH2Cl2/MeOH. Yield: 47 mg
(0.09 mmol, 95%) of purple crystals. Mp: 161 ꢀC; Rf¼0.96 (CH2Cl2:
n-hexane¼2: 1, v/v, silica gel, 6ꢂ3 cm); UV/vis (CH2Cl2): lmax (lg
CDCl3):
d
¼10.29 (s, 2H, Hmeso), 10.22 (s, 1H, Hmeso), 9.52e9.47 (m,
4H, Hb), 9.44 (AB, 3JHeH¼4.5 Hz, 2H, Hb), 9.19 (AB, 3JHeH¼4.5 Hz, 2H,
3
3
3
Hb), 8.17 (AB, JHeH¼8.7 Hz, 2H, Ph-H), 7.33 (AB, JHeH¼8.7 Hz, 2H,
(100%, [M]ꢃþ), 468 (86%, [MeC5H11]þ), 397 (50%, [Me2C5H11 ꢃþ),
]
Ph-H), 4.12 ppm (s, 3H, OCH3); 13C NMR (75 MHz, CDCl3):
135.61, 132, 112.19, 105.60, 105.47, 55.65 ppm; UV/vis (CH2Cl2): lmax
d
¼155.90,
270 (5%, [M]2þ), 234 (9%, [MeC5H11 2þ), 199 (13%,
]
[Me2C5H11]
2þ); HRMS (EI): m/z calcd for [C32H36N4Cu] 539.2236;
(lg
)¼404 (5.50), 532 (4.14), 563 nm (3.41); MS (EI, 220 ꢀC, 70 eV):
found 539.2209.
m/z¼478 (100%, [M]ꢃþ), 463 (9%, [MeCH3]þ); HRMS (EI): m/z calcd
for [C27H18N4OZn] 478.0772; found 478.0761.
4.4.20. (5,15-Dihexylporphyrinato)zinc(II) (Zn(II)3d). The free base
porphyrin H23d (250 mg, 0.52 mmol) was reacted with zinc(II)
acetate. The mixture was washed with several portions of water
and the organic layer was dried over sodium sulfate and filtered.
The solvent was removed under reduced pressure until crystals
were formed, which were recrystallization from CH2Cl2/MeOH.
Yield: 250 mg (0.462 mmol, 89%) of purple crystals. Mp: 285 ꢀC
(dec); Rf¼0.83 (CH2Cl2: n-hexane¼2: 1, v/v, silica gel, 6ꢂ3 cm); 1H
4.4.16. (5-(3,5-Di-tert-butyl)porphyrinato)nickel(II) (Ni(II)2h). The
free base porphyrin H22h (300 mg, 0.602 mmol) was dissolved in
toluene (30 mL) 100 mL RBF. The solution was heated to 120 ꢀC
before Ni(acac)2 (464 mg,1.806 mmol) was added. The reaction was
stirred at this temperature 4 h, monitoring via TLC control. The
reaction was then cooled to room temperature and solvents were
Please cite this article in press as: Senge, M. O.; et al., Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2015.11.008

10
M.O. Senge et al. / Tetrahedron xxx (2015) 1e11
NMR (400 MHz, CDCl3):
Hb), 9.43e9.42 (m, 4H, Hb), 5.05e5.01 (m, 4H, CH2), 2.57e2.55 (m,
4H, CH2), 1.86e1.83 (m, 4H, CH2), 1.58e1.39 (m, 8H, CH2),
d
¼10.23 (br s, 2H, Hmeso), 9.60e9.59 (m, 4H,
Methods or Patterson synthesis using the SHELXL PLUS program sys-
tem and refined against jF2j with the program SHELX using all data.25
Hydrogen atoms were fixed geometrically and allowed to ride on
ꢀ
0.97e0.94 ppm (m, 6H, CH3); UV/vis (CH2Cl2): lmax (lg
(5.58), 540 (4.17), 615 nm (3.76); MS (EI, 220 ꢀC, 70 eV) m/z: 540
(50%, [M]ꢃþ), 469 (100%, [MeC5H11]þ), 398 (84%, [Me2C5H11 ꢃþ),
200 (9%, [Me2C5H11
2þ); HRMS (EI): m/z calcd for [C32H36N4Zn]
540.2231; found 540.2205.
3
the parent carbon atoms, with aromatic CeH¼0.93 A, methylene
ꢀ
ꢀ
CeH¼0.97 A and methyl CeH¼0.97 A. The displacement parame-
ters were set for aromatic H atoms at Uiso(H)¼1.2 Ueq(C), methylene
H atoms at Uiso(H)¼1.2Ueq(C) and methyl H atoms at Uiso(H)¼1.5
]
]
Ueq(C).
4.4.21. {5,15-Bis(1-ethylpropyl)porphyrinato}copper(II)(Cu(II)3e). The
free base porphyrin H23e (50 mg, 0.12 mmol) was dissolved in
dichloromethane (60 mL) and mixed with methanol (25 mL), water
(3 drops) and copper acetate (67.5 mg, 0.37 mmol). The mixture
was stirred at rt for 2 h followed by filtration through silica gel
(CH2Cl2). Recrystallization from CH2Cl2/MeOH gave red crystals.
Yield: 35 mg (0.07 mmol, 63%). Mp: >310 ꢀC; Rf¼0.69 (CH2Cl2: n-
4.5.1. Crystal data andrefinement (Ni(II)2a). Crystal data: C24H20N4Ni,
M¼423.15, monoclinic, space group C2/c, a¼50.9305(18),
ꢀ
b¼6.5230(2), c¼11.5664(3) A,
a
¼90ꢀ,
b
¼95.7323(19)ꢀ,
g
¼90ꢀ,
3
ꢀ
V¼3823.4(2) A , Z¼8, T¼90K,
m
(MoKa)¼0.1033 cmꢁ1, 21,627 re-
flections measured, 5573 unique reflections measured (Rint¼0.1175),
276 parameters, 3007 reflections with I>2.0s(I), refinement against
jF2j, R1 (I>2.0
(I))¼0.0891, wR2 (all data)¼0.2850, S¼1.095,
s
hexane¼1: 2, v/v, silica gel); UV/vis (CH2Cl2): lmax (lg
3
rmax¼1.470. Refinement: Constraints and restraints were used to
model the disorder in the n-butyl chain C21eC24 (EADP, DFIX, ISOR,
SADI) and the model was refined to convergence. High residuals were
located near the Ni center.
530 (4.24), 567 nm (3.31); MS (EI, 70 eV): m/z¼516 (6%, [M] þ), 482
(8%, [MeC2H5]þ), 411 (13%, MeC7H16]þ), 396 (9%, MeC8H19]þ), 256
(13%, [M]2þ); HRMS (EI): m/z calcd for [C30H32CuN4] 511.1923; found
511.1907.
4.5.2. Crystal data and refinement (Zn(II)2e). Crystal data:
4.4.22. (5,15-Diphenylporphyrinato)nickel(II) (Ni(II)3f).14 The free
base porphyrin H23f (250 mg: 0.54 mmol) was reacted with nick-
el(II) acetate following the general procedure. Purification involved
recrystallization from CH2Cl2/MeOH. Yield: 220 mg (0.426 mmol,
79%) of purple crystals. Rf¼0.72 (CH2Cl2: n-hexane¼2: 1, v/v, silica
C
25H22N4Zn, M¼443.83, monoclinic, space group P21/c,
ꢀ
a¼14.4616(15), b¼12.1750(13), c¼11.9296(13) A,
a
¼90ꢀ,
3
ꢀ
ꢀ
b
¼112.684(2)ꢀ,
g
¼90 , V¼1938.0(4) A , Z¼4, T¼90K,
m
(MoKa)¼
0.1288 cmꢁ1, 17,123 reflections measured, 4456 unique reflections
measured (Rint¼0.0558), 274 parameters, 3348 reflections with
gel, 6ꢂ3 cm); (400 MHz: CDCl3)
d
¼9.96 (s, 2H, Hmeso), 9.21 (s, 4H,
I>2.0
s
(I), refinement against jF2j, R1 (I>2.0
(I))¼0.0376, wR2 (all
s
Hb), 8.96 (s, 4H, Hb), 8.07 (d, 4H, Ph-H), 7.77e7.73 ppm (m, 6H, Ph-
data)¼0.0940, S¼1.018, rmax¼1.521 Refinement: Residual electron
density was located in the side chain region, which shows higher
librational movement for some atoms. The close contacts are due
to the very tight dimeric packing of the molecules in the crystal.
H); UV/vis (CH2Cl2): lmax (lg
3
)¼400 (4.73), 515 (4.08), 547 nm
(3.79); MS (EI, 210 ꢀC, 70 eV): m/z¼518 (100%, [M]ꢃþ), 440 (20%,
[MeC6H6]ꢃþ), 259 (3%, [M]2þ). Other analytical data were as re-
ported in the literature.14
4.5.3. Crystal data and refinement (Zn(II)2f). Crystal data:
4.4.23. (5,15-Diphenylporphyrinato)copper(II) (Cu(II)3f).20 The free
base porphyrin H23f (250 mg, 0.54 mmol) was reacted with cop-
per(II) acetate following the general procedure. Purification in-
volved recrystallization from CH2Cl2/MeOH. Yield: 210 mg
(0.4 mmol, 75%) of purple crystals. Rf¼0.68 (CH2Cl2: n-hexane¼2: 1,
C
79H52N12Zn3, M¼1381.43, monoclinic, space group P21/c,
ꢀ
a¼28.441(3),
b¼1ꢀ8.5464(16),
c¼11.4645(10)
A,
a
¼90ꢀ,
3
ꢀ
b
¼91.320(2)ꢀ,
g
¼90 , V¼6045.7(9) A , Z¼4, T¼90K,
m(MoKa)¼
0.1243 cmꢁ1, 68,676 reflections measured, 13,846 unique re-
flections measured (Rint¼0.0769), 871 parameters, 9701 reflections
v/v, silica gel, 6ꢂ3 cm); UV/vis (CH2Cl2): lmax (lg
3 )¼403 (3.99), 526
with I>2.0
s
(I), refinement against jF2j, R1 (I>2.0
(I))¼0.0666, wR2
s
(3.69), 591 nm (3.41); MS (EI, 210 ꢀC, 70 eV): m/z¼523 (100%,
[M]ꢃþ), 445 (22%, [MeC6H6]ꢃþ), 260 (48%, [M]2þ), 223 (16%,
[MeC6H6]2þ). Other analytical data were as reported in the
literature.20
(all data)¼0.1925, S¼1.096, rmax¼1.483. Refinement: Structure was
refined as a two component twin. Restraints were used to model
the disordered solvent methanol molecules C1seC4s and O1seO4s
(DFIX) and the model was refined to convergence.
4.4.24. (5,15-Diphenylporphyrinato)zinc(II) (Zn(II)3f).20 The free
base porphyrin H23f (200 mg, 0.44 mmol) was reacted with zinc
acetate following the general procedure. Purification involved re-
crystallization from CH2Cl2/MeOH. Yield: 210 mg (0.41 mmol, 93%)
of purple crystals. Rf¼0.39 (CH2Cl2: n-hexane¼2: 1, v/v, silica gel,
4.5.4. Crystal data and refinement (Ni(II)2h). Crystal data:
C
69H65Cl3N8Ni2, M¼1230.06, orthorhombic, space group P212121,
ꢀ
a¼11.0604(4), b¼25.9552(8), c¼41.0751(13) A,
a
¼90ꢀ,
b
¼90ꢀ,
3
ꢀ
ꢀ
g
¼90 , V¼11,790.3(7) A , Z¼8, T¼100K,
m
(MoKa)¼0.0825 cmꢁ1
,
1,31,133 reflections measured, 23,278 unique reflections measured
6ꢂ3 cm); (400 MHz: CDCl3)
d
¼10.34 (s, 2H, Hmeso), 9.47 (d,
(Rint¼0.0434), 1595 parameters, 20,473 reflections with I>2.0
s
(I),
3
3JHeH¼4.64 Hz, 4H, Hb), 9.18 (d, JHeH¼4.64 Hz, 4H, Hb), 8.30 (dd,
3JHeH¼1.16, 2.32 Hz, 4H, Ph-H), 7.85e7.82 ppm (m, 6H, Ph-H); UV/
refinement against jF2j, R1 (I>2.0
s
(I))¼0.0374, wR2 (all data)¼
0.0835, S¼1.037, rmax¼1.386. Refinement: Refined as a two com-
ponent inversion twin. Restraints were used (ISOR) to model the
disorder tert-butyl groups over two positions each with occupan-
cies of 79, 68 and 65% for the major moieties and refined to con-
vergence. Solvent molecules were found packed between
porphyrin layers.
vis (CH2Cl2): lmax (lg
3
)¼407 (4.84), 536 (3.66), 571 nm (2.97); MS
(EI, 210 ꢀC, 70 eV): m/z¼524 (100%, [M]ꢃþ), 446 (19%, [MeC6H6]ꢃþ),
262 (21%, [M]2þ). Other analytical data were as reported in the
literature.20
4.5. Single crystal X-ray structure determinations
Growth and handling of crystals followed the concept de-
veloped by Hope.24 The intensities were corrected for Lorentz,
polarization and absorption effects. Nonhydrogen atoms were re-
fined with anisotropic thermal parameters, and hydrogen atoms
were placed into geometrically calculated positions and refined
using a riding model. The structures were solved with Direct
4.6. Normal structural decomposition (NSD) analysis
The overall degree of distortion and the contributions of in-
dividual distortion modes were determined using the normal
structural decomposition method developed by Shelnutt and co-
workers.20 NSD classifies the distortions in terms of equivalent
Please cite this article in press as: Senge, M. O.; et al., Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2015.11.008

M.O. Senge et al. / Tetrahedron xxx (2015) 1e11
11
€
8. Brinas, R. P.; Bruckner, C. Tetrahedron 2002, 58, 4375e4381.
displacements along the normal coordinates and illustrates the mix
of distortion modes present in porphyrins.
9. (a) Fang, Y.; Senge, M. O.; Van Caemelbecke, E.; Smith, K. M.; Medforth, C. J.;
Zhang, M.; Kadish, K. M. Inorg. Chem. 2014, 53, 10772e10778; (b) Reddy, M. H.
V.; Al-Shammari, R. M.; Al-Attar, N.; Kennedy, E.; Rogers, L.; Lopez, S.; Senge, M.
O.; Keyes, T. E.; Rice, J. H. Phys. Chem. Chem. Phys. 2014, 16, 4386e4393; (c)
Reddy, H. V.; Al-Shammari, R. M.; Al-Attar, N.; Rogers, L.; Lopez, S.; Forster, R. J.;
Senge, M. O.; Keyes, T. E.; Rice, J. H. Chem. Phys. Mater. 2014, 143, 963e968.
10. Senge, M. O.; Shaker, Y. M.; Pintea, M.; Ryppa, C.; Hatscher, S. S.; Ryan, A.;
Sergeeva, Y. Eur. J. Org. Chem. 2010, 237e258.
Acknowledgements
This work was supported by a grant from Science Foundation
Ireland (SFI IvP 13/IA/1894 SFI). We are indebted to Dr. J. Fettinger
and Prof. M. M. Olmstead (UC Davis) for help with some of the data
collections.
11. Senge, M. O.; Dahms, K.; Holdt, H.-J.; Kelling, A. Z. Naturforsch. 2015, 70b,
119e123.
12. (a) Song, X.-Z.; Jentzen, W.; Jaquinod, L.; Khoury, R. G.; Medforth, C. J.; Jia, S.-L.;
Ma, J.-G.; Smith, K. M.; Shelnutt, J. A. Inorg. Chem. 1998, 37, 2117e2128; (b)
Senge, M. O. Acta Cryst. 2011, C67, m39em42.
13. (a) Buchler, J. W. In The Porphyrins; Dolphin, D., Ed.; Academic: New York, 1978;
Vol. 1, pp 389e483; (b) Speck, M.; Niethammer, D.; Senge, M. O. J. Chem. Soc.
Perkin Trans. 2 2002, 455e462.
14. Song, X.-Z.; Jentzen, W.; Jia, S.-L.; Jaquinod, L.; Nurco, D. J.; Medforth, C. J.;
Smith, K. M.; Shelnutt, J. A. J. Am. Chem. Soc. 1996, 118, 12975e12988.
15. (a) Rothemund, P. J. Am. Chem. Soc. 1935, 57, 2010e2011; (b) Volz, H.; Herb, G. Z.
Naturforsch. 1983, 38b, 1240e1242; (c) Senge, M. O.; Bischoff, I.; Nelson, N. Y.;
Smith, K. M. J. Porphyr. Phthalocyanines 1999, 3, 99e116.
16. Senge, M. O.; Forsyth, T. P.; Smith, K. M. Z. Krist. 1996, 211, 176e185.
17. Kozlowski, P. M.; Bingham, J. R.; Jarzecki, A. A. J. Phys. Chem. A 2008, 112,
12781e12788.
Supplementary data
CCDC 1414355 (Ni(II)2a), 1414356 (Zn(II)2e), 1414357 (Zn(II)2f)
and 1414358 (Ni(II)2h) contain the supplementary crystallographic
data for this paper. These data can be obtained free of charge from
The Cambridge Crystallographic Data Centre via www.ccdc.cam.a-
c.uk/data_request/cif.
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Please cite this article in press as: Senge, M. O.; et al., Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2015.11.008