Porphyrazines as molecular scaffolds: Flexible syntheses of novel multimetallic complexes

Article abstract of DOI:10.1021/ic060176n

Reductive deselenation of selenodiazole-fused porphyrazines, followed by acylation of the resultant labile porphyrazinediamines, was used to prepare macrocycles bearing two Collins ligands, two oxamido residues, or two quinoline-2-carboxamido units. Peripheral coordination of copper(II) to the di-(quinoline-2-carboxamido)-porphyrazine gave a metal-linked face-to-face porphyrazine dimer array. Sequential derivatization of the two amino groups in the porphyrazinediamines was used to prepare mixed peripheral ligand systems including a dimetallic picolinamido-Schiff base porphyrazine. Such systems exhibit strong metal-metal spin coupling and are anticipated to be of value in the synthesis of novel electronic and magnetic materials.

Full text of DOI:10.1021/ic060176n

Inorg. Chem. 2006, 45, 3686−3694
Porphyrazines as Molecular Scaffolds: Flexible Syntheses of Novel
Multimetallic Complexes
Tomasz Goslinski,† Chang Zhong,‡ Matthew J. Fuchter,† Charlotte L. Stern,‡ Andrew J. P. White,†
Anthony G. M. Barrett,*,† and Brian M. Hoffman*,‡
Department of Chemistry, Imperial College, London SW7 2AZ, England, and
Department of Chemistry, Northwestern UniVersity, EVanston, Illinois 60208
Received January 31, 2006
Reductive deselenation of selenodiazole-fused porphyrazines, followed by acylation of the resultant labile
porphyrazinediamines, was used to prepare macrocycles bearing two Collins ligands, two oxamido residues, or
two quinoline-2-carboxamido units. Peripheral coordination of copper(II) to the di-(quinoline-2-carboxamido)-
porphyrazine gave a metal-linked face-to-face porphyrazine dimer array. Sequential derivatization of the two amino
groups in the porphyrazinediamines was used to prepare mixed peripheral ligand systems including a dimetallic
picolinamido−Schiff base porphyrazine. Such systems exhibit strong metal−metal spin coupling and are anticipated
to be of value in the synthesis of novel electronic and magnetic materials.
Introduction
systems exhibit electron transfer or magnetic exchange
between the metal ion in the macrocyclic cavity and the metal
ion or ions bound by the peripheral bidentate S2, N2, or O2
ligand units.10,12,15
Polydentate ligands capable of binding multiple metal ions
are of considerable interest because their derivatives are of
value in the study of electron-transfer processes,1 macrocycle-
mediated spin coupling,2-4 ultrahigh-spin molecules,5 and
biomimetic chemistry.6 Previously, we have reported the
synthesis of porphyrazines (pzs) bearing multiple thiol,
amine, or alcohol peripheral substituents, along with their
conversion to multimetallic coordination complexes.7-14 Such
More recently, we have investigated an alternative ap-
proach to peripheral metal coordination by the fusion of salen
and other polydentate ligands to the porphyrazine ring. For
example, we have described the preparation of a phenan-
throline-appended porphyrazine and its conversion to a
variety of Ru(II) complexes including a ruthenium-linked
porphyrazine trimer.16 We have also reported the preparation
of porphyrazine-Schiff base systems,17 along with their
conversion into M1[pz]-M2[Schiff base] complexes.18 Fol-
lowing our initial reports of the spin coupling between metal
ions in these novel dimetallic systems,17,18 a detailed
* To whom correspondence should be addressed. E-mail: agmb@
imperial.ac.uk (A.G.M.B.); bmh@northwestern.edu (B.M.H.).
† Imperial College London.
‡ Northwestern University.
(1) Electron Transfer and Radical Processes in Transition Metal Chem-
istry; Astruc, D., Ed.; VCH Publishers: New York, 1995.
(2) Zhong, C.; Zhao, M.; Stern, C.; Barrett, A. G. M.; Hoffman, B. M.
Inorg. Chem. 2005, 44, 8272.
(3) Kahn, O. Molecular Magnetism; VCH Publishers: New York, 1993.
(4) Attia, A. S.; Conklin, B. J.; Lange, C. W.; Pierpont, C. G. Inorg. Chem.
1996, 35, 1033.
(11) Goldberg, D. P.; Michel, S. L.; White, A. J. P.; Williams, D. J.; Barrett,
A. G. M.; Hoffman, B. M. Inorg. Chem. 1998, 37, 2100.
(12) Goldberg, D. P.; Montalban, A. G.; White, A. J. P.; Williams, D. J.;
Barrett, A. G. M.; Hoffman, B. M. Inorg. Chem. 1998, 37, 2873.
(13) Lange, S. J.; Nie, H.; Stern, C. L.; Barrett, A. G. M.; Hoffman, B. M.
Inorg. Chem. 1998, 37, 6435.
(5) Goldberg, D. P.; Koulougliotis, D.; Brudvig, G. W.; Lippard, S. J. J.
Am. Chem. Soc. 1995, 117, 3134.
(6) Sessler, J. I.; Sibert, J. W.; Lynch, V.; Markert, J. T.; Wooten, C. I.
Inorg. Chem. 1993, 32, 621.
(7) Vela´zquez, C. S.; Fox, G. A.; Broderick, W. E.; Anderson, K. A.;
Anderson, O. P.; Barrett, A. G. M.; Hoffman, B. M. J. Am. Chem.
Soc. 1992, 114, 7416.
(8) Vela´zquez, C. S.; Baumann, T. F.; Olmstead, M. M.; Hope, H.; Barrett,
A. G. M.; Hoffman, B. M. J. Am. Chem. Soc. 1993, 115, 9997.
(9) Baumann, T. F.; Nasir, M. S.; Sibert, J. W.; White, A. J. P.; Olmstead,
M. M.; Williams, D. J.; Barrett, A. G. M.; Hoffman, B. M. J. Am.
Chem. Soc. 1996, 118, 10479.
(14) Cook, A. S.; Williams, D. B. G.; White, A. J. P.; Williams, D. J.;
Lange, S. J.; Barrett, A. G. M.; Hoffman, B. M. Angew. Chem., Int.
Ed. 1997, 36, 760.
(15) Michel, S. L.; Baum, S.; Barrett, A. G. M.; Hoffman, B. M. In Progress
in Inorganic Chemistry; Karlin, K. D., Ed.; Wiley & Sons: New York,
2001; Vol. 50, pp 473.
(16) Montalban, A. G.; Sakellariou, E. G.; Riguet, E.; McCubbin, Q. J.;
Barrett, A. G. M.; Hoffman, B. M. Inorg. Chim. Acta 2001, 317, 143.
(17) Zhao, M.; Stern, C.; Barrett, A. G. M.; Hoffman, B. M. Angew. Chem.,
Int. Ed. 2003, 42, 462.
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B. M. J. Am. Chem. Soc. 2001, 123, 4741.
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3686 Inorganic Chemistry, Vol. 45, No. 9, 2006
10.1021/ic060176n CCC: $33.50
© 2006 American Chemical Society
Published on Web 04/01/2006

Porphyrazines as Molecular Scaffolds
(FAB): m/z 1276 (M + H)+. MS (MALDI): 1276.2 (M + H)+.
[C78H84N10OSeZn]0.5‚[C79H86N10OSeZn]0.5‚[C3H8O]1.75: M )
1434.06. Crstal data: triclinic; P1h; a ) 14.884(2), b ) 18.786(3),
c ) 29.167(4) Å; R ) 80.101(12), â ) 82.475(13), γ ) 86.301-
(12)°; V ) 7957(2) Å3; Z ) 4; Dc ) 1.197 g cm-3; µ(Cu KR) )
1.355 mm-1; T ) 173(2) K; 71 401 reflections collected; F2
refinement; R1 ) 0.1378, R2 ) 0.3317; 9494 observed reflections
[|Fo| > 4σ(|Fo|), 2θ ) 142.48°]; 1887 parameters.
comparison of several derivatives, [CuII-CuII], [CuII-VIVO],
[ClMnIII-CuII], and [ClMnIII-VIVO], was carried out. This
study related the ligand-mediated exchange coupling to the
relative symmetries of the “magnetic orbits” and the influence
of π-exchange.19
Herein we report the synthesis of a range of porphyrazines
bearing several alterative peripheral multidentate ligands
including vicinal di-(2-hydroxy-2-methylpropanamido), di-
(2-methoxy-2-oxo-acetamido), di-(2-pyridine-carboxamido),
and di-(2-quinolinecarboxamido) units. This study is an
extension of our recent reports of metal ion coordination by
di-(2-pyridine-carboxamido)-porphyrazines,2 multidentate
ligands combining porphyrazines with the Vagg system.20
[7,8,12,13,17,18-Hexapropyl-2,3-di-(2-hydroxy-2-methylpro-
panamido)porphyrazinato]zinc(II) (8). H2S was bubbled through
porphyrazine 1a (50 mg, 0.072 mmol) in anhydrous pyridine (50
mL) for 5 min, during which time the blue solution turned violet.
AcOCMe2COCl (0.6 mL, 3.6 mmol) was added with stirring at 0
°C. After 2 h at room temperature, the solution was rotary
evaporated, and the residue was dissolved in trifluoroacetic acid
(4 mL). After 10 min, the mixture was poured into iced water,
neutralized with saturated aqueous NaHCO3, and extracted with
CH2Cl2 (50 mL), and then the organic phase was dried and
evaporated. Chromatography (CHCl3) gave porphyrazine 6 (38 mg,
65%). UV-vis (CH2Cl2): λmax (log ꢀ) 347 (4.74), 572 (4.48), 631
(4.18) nm. MS (APCI): m/z 853 (M + H)+. It was used directly
without further purification. Crude porphyrazine 6 (54 mg, 0.062
mmol) and Zn(OAc)2 (135 mg, 0.62 mmol) in THF and MeOH
(1:1, 50 mL) were heated to reflux with stirring for 3 h. Rotary
evaporation and chromatography (MeOH/CHCl3 1:200) gave por-
phyrazine 7 (53 mg, 94%). IR (film): 3422, 1744, 1663, 1521,
1464, 1147 cm-1. UV-vis (CH2Cl2): λmax 345, 604 nm. 1H NMR
(400 MHz, d5-pyridine): δ 10.3 (br s, 2H), 3.58-3.72 (m, 12H),
2.18 (s, 6H), 2.02-2.16 (m, 12H), 1.86 (s, 12H), 0.92-1.12 (m,
18H). MS (APCI): 915 (M + H)+. Deoxygenated MeOH (40 mL)
was added to crude porphyrazine 7 (53 mg, 0.058 mmol), K2CO3
(40 mg), and NaOMe (ca. 5 mg) (Schlenk flask), and the mixture
was stirred at ambient temperature for 18 h. Rotary evaporation
and chromatography (CH2Cl2/MeOH 50:1) gave porphyrazine 8 (39
mg, 80%): mp > 300 °C (DMSO). IR (film): 3425, 1643, 1383,
Experimental Section
[7,8,12,13,17,18-Hexapropyl-[1,2,5]selenadiazolo[3,4-q]por-
phyrazinato]zinc(II) (3a). Porphyrazine 2a (72 mg, 0.11 mmol;
prepared from porphyrazine 1a),21 Zn(OAc)2 (37 mg, 0.17 mmol),
and anhydrous DMF (40 mL) were heated with stirring at 100 °C
for 18 h. Rotary evaporation and chromatography (MeOH/CH2Cl2
1:50) gave porphyrazine 3a (66 mg, 83%) as a green solid: mp >
300 °C (pyridine), Rf ) 0.52 (MeOH:CH2Cl2 1:25). IR (film): 1688,
1470, 1145, 1009 cm-1. UV-vis (CH2Cl2): λmax (log ꢀ) 341 (5.69),
1
354 (5.73), 595 (5.48), 638 (5.59) nm. H NMR (400 MHz, d5-
pyridine): δ 4.07-4.13 (m, 12H), 2.47-2.56 (m, 12H), 1.37-1.42,
1.24-1.28 (m, t, J ) 7.3 Hz, 18H). 13C NMR (100 MHz,
d5-pyridine): δ 171.6, 159.5, 158.0, 157.8, 145.7, 145.2, 144.2,
144.0, 28.8, 28.7, 28.4, 26.1, 26.1, 25.9, 15.1, 14.8. MS (FAB):
m/z 735 (M + H)+. HRMS (FAB) Calcd for C34H43N10SeZn: (M
+ H)+ 735.2129. Found: (M + H)+. 735.2104. Crystal data:
C34H42N10SeZn‚C5H5N; M ) 814.21; triclinic; P1h; a ) 10.2170-
(9), b ) 15.4684(13), c ) 26.108(2) Å; R ) 82.207(7), â ) 83.440-
(7), γ ) 70.071(8)°; V ) 3833.0(6) Å3; Z ) 4; Dc ) 1.411 g cm-3
;
µ(Cu KR) ) 1.635 mm-1; T ) 173(2) K; 37570 reflections
collected; F2 refinement; R1 ) 0.0756, R2 ) 0.1673; 22 706
observed reflections [|Fo| > 4σ(|Fo|), 2θ ) 65.08°]; 1024 param-
eters.
1
1095 cm-1. UV-vis (CH2Cl2): λmax 345, 604 nm. H NMR (400
MHz, d6-DMSO): δ 10.9 (br m, 2H), 3.76-3.86 (m, 12H), 2.24-
2.34 (m, 12H), 1.66 (s, 12H), 1.18-1.28 (m, 18H). MS (APCI):
m/z 831 (M + H)+. C44H64N10O5SZn‚C2H6O: M ) 956.55. Crstal
data: triclinic; P1h; a ) 11.170(3), b ) 16.138(4), c ) 16.255(4)
Å; R ) 115.726(3), â ) 95.645(4), γ ) 100.672(4)°; V ) 2540.7-
(10) Å3; Z ) 2; Dc ) 1.250 g cm-3; µ(Mo KR) ) 0.579 mm-1; T
) 153(2) K; 23 380 reflections collected; F2 refinement; R1 )
0.0737, R2 ) 0.2107; 11 882 observed reflections [2θ ) 57.68°];
599 parameters.
[7,8,12,13,17,18-Hexa-(4-tert-butylphenyl)-[1,2,5]selenadiazolo-
[3,4-q]porphyrazinato]zinc(II) (3b). Porphyrazine 2b (468 mg,
0.39 mmol; prepared from 3,4-dicyano-1,2,5-selenodiazole22 and
3,4-di-(4-tert-butylphenyl)pyrroline-2,5-diimine via porphyrazine
1b13 following the procedure of Baum et al.),21 Zn(OAc)2 (108 mg,
0.59 mmol), and anhydrous DMF (120 mL) were heated with
stirring at 100 °C for 18 h. Rotary evaporation and chromatography
(MeOH/CH2Cl2 1:50) gave porphyrazine 3b (418 mg, 85%) as a
green solid: mp > 300 °C (CHCl3/EtOH/ClCH2CH2Cl/PrOH), Rf
) 0.78 (MeOH/CH2Cl2 1:50). IR (film): 1474, 1362, 1100, 977
cm-1. UV-vis (CH2Cl2/MeOH 25:1): λmax (log ꢀ) 366 (4.77),
611 (4.54), 676 (4.77) nm. 1H NMR (400 MHz, d5-pyridine):
δ 8.77-8.68, 7.78-7.72 (2m, 6H, overlapping solvent pyridine),
1.48, 1.47, 1.36 (3s, 27H). 13C NMR (125 MHz, d5-pyridine): δ
171.3, 159.3, 157.0, 156.8, 151.0, 147.9, 142.9, 142.2, 141.7, 133.3,
132.4, 132.2, 126.0, 125.8, 35.0, 34.9, 31.6, 31.4, 30.0. MS
[7,8,12,13,17,18-Hexapropyl-2-amino-3-(2-pyridinecarbox-
amido)porphyrazinato]iron(III) chloride (12). Porphyrazine 112
(50 mg, 0.062 mmol), FeBr2 (135 mg, 0.62 mmol), and 2,6-lutidine
(2 mL) in THF and PhMe (1:1, 50 mL) were heated with stirring
at 100 °C for 20 h. The conversion was monitored by UV-vis
spectroscopy. After rotary evaporation, the residue was dissolved
in CH2Cl2 (40 mL), and aqueous 1 M HCl (40 mL) added. After
30 min, the separated organic layer was washed with brine, dried,
rotary evaporated, and chromatographed (CH2Cl2/MeOH 50:1) to
give porphyrazine 12 (20 mg, 40%). IR (film): 3286, 1673, 1634,
1500, 1151 cm-1. UV-vis (CH2Cl2): λmax 317, 375, 564 nm.
MS(ESI): m/z Calcd for (M - Cl)+ C40H49FeN11O: (M - Cl)+
755.3. Found: (M - Cl)+, 755.5.
(19) Zhao, M.; Zhong, C.; Stern, C.; Barrett, A. G. M.; Hoffman, B. M. J.
Am. Chem. Soc. 2005, 127, 9769.
(20) Barnes, D. J.; Chapman, R. L.; Vagg, R. S.; Watton, E. C. J. Chem.
Eng. Data 1978, 23, 349.
[7,8,12,13,17,18-Hexapropyl-2,3-di-((methoxycarbonyl)car-
boxamido)porphyrazinato]zinc(II) (13). H2S was bubbled through
Zn[pz(Pr)6(N2Se)] 3a (116 mg, 0.16 mmol) in anhydrous pyridine
(20 mL) for 150 s, during which time the blue color intensified.
MeO2CCOCl (2 × 150 µL, 1.6 mmol) was added in 2 portions
(21) Baum, S.; Trabanco, A. A.; Montalban, A. G.; Micallef, A. S.; Zhong,
C.; Meunier, H. G.; Suhling, K.; Philips, D.; White, A. J. P.; Williams,
D. J.; Barrett, A. G. M.; Hoffman, B. M. J. Org. Chem. 2003, 68,
1665.
(22) Bauer, E. M.; Ercolani, C.; Galli, P.; Popkova, I. A.; Stuzhin, P. A. J.
Porphyrins Phthalocyanines 1999, 3, 371.
Inorganic Chemistry, Vol. 45, No. 9, 2006 3687

Goslinski et al.
over 1 h, and the mixture was stirred at ambient temperature for 4
h. Pyridine was removed by distillation to leave a crude residue
containing 5a, which was further washed with hexanes (40 mL)
and chromatographed (CH2Cl2/MeOH 50:1) to give porphyrazine
9: Rf 0.47 (MeOH/CH2Cl2 1:50). MS(FAB+): m/z 745 (M+•).
HRMS (FAB+) Calcd for C37H49N10O3Zn: (M + H)+ 745.3281.
Found: (M + H)+ 745.3288. MeO2CCOCl (2 × 150 µL, 1.6 mmol)
was added, with stirring, in two portions to porphyrazine 9 in
pyridine (15 mL) over 1 h. The mixture was stirred at ambient
temperature overnight. MeOH (1 mL) was added, and the mixture
was stirred for a further 30 min. Rotary evaporation gave a residue,
which was washed with hexanes (20 mL) and chromatographed
(CH2Cl2/MeOH 50:1, CH2Cl2/MeOH/Et3N 50:1:0.1) to give por-
phyrazine 13 (38 mg, 29%) as blue solid: Rf ) 0.28 (MeOH/
CH2Cl2 1:50), Rf ) 0.50 (EtOAc/hexanes 1:1). IR (film): 3216,
1727, 1682, 1532, 1463, 1306, 1152, 1013 cm-1. UV-vis
(CH2Cl2): λmax (log ꢀ) 346 (4.77), 596 (4.64), 612 (4.73), 649 (4.04)
) 1.276 g cm-3; µ(Cu KR) ) 0.449 mm-1; T ) 173(2) K; deep
red blocks; 33 011 reflections collected; F2 refinement; R1 ) 0.0823,
R2 ) 0.1905; 19 487 observed reflections [|Fo| > 4σ(|Fo|), 2θ )
65.38°]; 808 parameters. Porphyrazine 15a showed the following
data: Rf ) 0.92 (MeOH/CH2Cl2 1:25). IR (film): 3287, 1691, 1524,
1146, 770 cm-1. UV-vis (CH2Cl2/MeOH 25:1): λmax (log ꢀ) 241
(4.78), 345 (4.75), 573 (4.51), 631 (4.65) nm. 1H NMR (400 MHz,
d5-pyridine/CDCl3 1:1): δ 13.01 (s, 2H), 8.88 (d, J ) 8.4 Hz, 2H,
overlapped with pyridine), 8.77 (d, J ) 8.4 Hz, 2H), 8.57 (m, 2H),
8.17 (d, J ) 7.5 Hz, 2H, overlapped with pyridine), 7.92 (d, J )
7.0 Hz, 2H), 4.37, 4.30, 4.14 (3t, J ) 8 Hz, 12H), 2.78, 2.67 (2 m,
12H), 1.51-1.68, (m, 18H). MS (FAB): m/z 907 (M + H)+. HRMS
(FAB) Calcd for C54H59N12O2: (M + H)+ 907.4884. Found: (M
+ H)+ 907.4863.
[7,8,12,13,17,18-Hexa-(4-tert-butylphenyl)-2,3-di-(quinoline-
2-carboxamido)porphyrazinato]zinc(II) (14b). H2S was bubbled
through porphyrazine 3b (36 mg, 0.028 mmol) in anhydrous
pyridine (8 mL) for 2 min. 2-Quinolinecarbonyl chloride (54 mg,
0.28 mmol) suspended in PhMe (2 mL) was added, and the mixture
was stirred at ambient temperature for 4 h. MeOH (3 mL) was
added to the solution containing crude 5b, and the resulting mixture
was stirred for 30 min. Pyridine was removed by distillation to
leave a crude residue, which was washed with hexanes and
chromatographed (CH2Cl2/MeOH 10:1) to give porphyrazine 10b.
MS (FAB): m/z 1355 (M+•). MS (MALDI): m/z 1355.5 (M+•).
Porphyrazine 10b and 2-quinolinecarbonyl chloride (54 mg, 0.28
mmol) in pyridine (8 mL) were stirred for 18 h at ambient
temperature. The pyridine was removed by distillation, and the
residue washed with hexanes (50 mL) and chromatographed
(CH2Cl2/MeOH 25:1 and 50:1) to give porphyrazine 15b (18 mg,
44%) as a violet product and porphyrazine 14b (14 mg, 34%) as a
green product. Porphyrazine 14b showed the following data: mp
> 300 °C (CHCl3/EtOH/ClCH2CH2Cl/iPrOH), Rf ) 0.78 (MeOH/
CH2Cl2 1:50). IR (film): 3443, 1716, 1604, 1501, 1372, 1267, 1107,
978, 839, 769 cm-1. UV-vis (CH2Cl2/MeOH 50:1): λmax (log ꢀ)
1
nm. H NMR (500 MHz, d5-pyridine): δ 9.74 (br s, 2H), 4.00-
4.09 (m, 12H), 3.90 (s, 6H), 2.46-2.55 (m, 12H), 1.29-1.41, (m,
18H). 13C NMR (125 MHz, d5-pyridine): δ 162.0, 160.0, 159.8,
158.9, 154.6, 150.4, 145.0, 144.7, 144.6, 127.0, 53.5, 30.0, 28.6,
26.0, 15.1, 15.03, 14.99. MS (FAB): m/z 831 (M + H)+. HRMS
(FAB) Calcd for C40H51N10O6Zn: (M + H)+ 831.3284. Found: (M
+ H)+ 831.3319.
[7,8,12,13,17,18-Hexapropyl-2,3-di-(quinoline-2-carboxami-
do)porphyrazinato]zinc(II) (14a). H2S was bubbled through
porphyrazine 3a (121 mg, 0.165 mmol) in anhydrous pyridine (20
mL) for 150 s, during which time the blue color intensified.
2-Quinolinecarbonyl chloride (316 mg, 1.65 mmol) suspended in
PhMe (5 mL) was added, and the mixture was stirred at ambient
temperature for 4 h, during which time the color changed from
blue to blue-green. MeOH (1 mL) was added, and stirring was
continued for 30 min. Pyridine was removed by distillation, and
the residue was chromatographed (CH2Cl2/MeOH 10:1) to give
porphyrazine 10a: Rf 0.87 (MeOH/CH2Cl2 1:25). MS (FAB+): m/z
814 (M + H)+. HRMS (FAB+) Calcd for C44H52N11OZn: (M +
H)+ 814.3648. Found: (M + H)+ 814.3627. Porphyrazine 10a and
2-quinolinecarbonyl chloride (316 mg, 1.65 mmol) in pyridine (20
mL) were stirred for 18 h at ambient temperature. MeOH (1 mL)
was added to the mixture, and stirring was continued for 30
min. Pyridine was removed by distillation to leave a crude resi-
due, which was washed with hexanes (50 mL) and chromato-
graphed (CH2Cl2/MeOH 50:1) to give porphyrazine 15a (8 mg,
5%) as a violet solid and porphyrazine 14a (69 mg, 43%) as a
green product. Porphyrazine 14a showed the following data: mp
> 300 °C (pyridine/CH2Cl2/MeOH), Rf ) 0.61 (MeOH/CH2Cl2
1:25). IR (film): 3387, 1716, 1682, 1147, 1032, 769 cm-1. UV-
vis (CH2Cl2/MeOH 25:1): λmax (log ꢀ) 239 (3.81), 350 (4.66), 616
(4.54) nm. 1H NMR (400 MHz, d5-pyridine): δ 13.12 (s, 2H), 8.75
(d, J ) 8.4 Hz, 2H), 8.68 (d, J ) 8.7 Hz, 2H, overlapping with
solvent pyridine), 8.37 (d, J ) 8.4 Hz, 2H), 8.00 (t, J ) 8.1 Hz,
2H), 7.93 (d, J ) 8.1 Hz, 2H), 7.85 (d, J ) 7.8 Hz, 2H), 7.68 (t,
J ) 7.9 Hz, 2H), 4.18, 4.10 (t, J ) 7.5 Hz, t J ) 7.3 Hz, 12H),
2.69, 2.67 (2m, 12H), 1.48, 1.42-1.35, 1.26 (t, 2m, J ) 7.2 Hz,
18H). 13C NMR (100 MHz, d5-pyridine): δ 162.5, 159.2, 159.1,
152.2, 151.2, 150.8, 147.0, 144.7, 144.6, 144.3, 138.3, 137.8,
131.0, 130.4, 130.0, 129.9, 129.6, 128.7, 128.5, 128.3, 126.9,
119.5, 119.4, 30.0, 29.7, 28.9, 28.7, 26.2, 26.1, 24.5, 15.4, 15.1,
15.0. MS (FAB): m/z 969 (M + H)+. HRMS (FAB) Calcd for
C54H57N12O2Zn: (M + H)+ 969.4019. Found: (M + H)+ 969.4040.
Crystal data: C59H61N13O2Zn‚2C5H5N; M ) 1207.78; triclinic; P1h;
a ) 12.1703(5), b ) 15.7922(7), c ) 17.5468(7) Å; R ) 90.108-
(3), â ) 90.338(3), γ ) 111.202(4)°; V ) 3144.1(2) Å3; Z ) 2; Dc
1
374 (4.82), 641 (4.85) nm. H NMR (400 MHz, d5-pyridine): δ
12.73 (s, 2H), 8.85 (d, J ) 8.3 Hz, 2H), 8.68 (overlapping solvent
pyridine), 8.42 (d, J ) 8.4 Hz, 2H), 8.02 (m, 2H), 7.78 (m, 2H),
7.70 (d, J ) 8.4 Hz, 2H), 7.38 (m, 2H), 1.48, 1.47, 1.20 (3s, 54H).
MS (FAB): m/z 1511 (M+•). MS (MALDI): m/z 1512.0 (M +
H)+. Crystal data: [C101H97N13O2Zn]0.85‚[C96H92N12O2Zn]0.15‚
[C5H5N]0.25‚[C3H8O]0.25; M ) 1613.22; triclinic; P1h; a )
14.4592(19), b ) 18.004(4), c ) 19.772(2) Å; R ) 97.654(16), â
) 100.365(10), γ ) 112.803(14)°; V ) 4549.1(12) Å3; Z ) 2; Dc
) 1.178 g cm-3; κ(Cu KR) ) 0.813 mm-1; T ) 173(2) K; 41 945
reflections collected; F2 refinement; R1 ) 0.1486, R2 ) 0.3432;
8763 observed reflections [|Fo| > 4σ (|Fo|), 2θ ) 142.36°]; 1181
parameters. Porphyrazine 15b showed the following data: Rf )
0.94 (MeOH/CH2Cl2 1:50). IR (film): 3286, 1684, 1516, 1487,
1267, 1108, 953 cm-1. UV-vis (CH2Cl2): λmax (log ꢀ) 367 (4.88),
1
468 (4.44), 599 (4.64), 677 (4.90) nm. H NMR (400 MHz, d5-
pyridine): δ 12.72 (s, 2H), 8.45, 8.03, 7.79 (3 br s, 12H, overlapping
solvent pyridine), 1.49, 1.27, 0.85 (3 s, 54H). MS (FAB): m/z 1448
(M+•). MS (MALDI): m/z 1449.3 (M + H)+.
N′,N′,N′′,N′′-Dicopper(II) Di-([7,8,12,13,17,18-hexapropyl-2,3-
di-(quinoline-2-carboxamido)porphyrazinato])zinc (II) (18a).
1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) (11 µL, 0.074 mmol)
in DMF (1 mL) was added to porphyrazine 14a (33 mg, 0.034
mmol) in DMF (5 mL). After 10 min, CuCl2 (9.9 mg, 0.074
mmol) in DMF (1 mL) was added, and the mixture was stirred for
24 h at ambient temperature. Rotary evaporation and chromatog-
raphy (CH2Cl2/MeOH 10:1) gave complex 18a (13 mg, 37%):
mp > 300 °C (HOCH2CH2OH/ClCH2CH2Cl/EtOH), Rf ) 0.28
3688 Inorganic Chemistry, Vol. 45, No. 9, 2006

Porphyrazines as Molecular Scaffolds
Scheme 1 a
a Reagents and conditions: (a) CF3CO2H, 20 °C, 20 min; (b) Zn(OAc)2, DMF, 100 °C, 18 h (83-85%); (c) H2S, pyridine, 20 °C, 2-5 min; (d) (i)
AcOC(Me)2COCl, pyridine, 0 °C to 20 °C, 2 h, (ii) CF3CO2H, 20 °C, 20 min (65%); (e) Zn(OAc)2, THF, MeOH, ∆, 3 h (94%); (f) K2CO3, NaOMe, MeOH,
20 °C, 18 h (80%).
(MeOH/CH2Cl2 1:25). IR (film): 3396, 1625, 1462 cm-1
.
tion and chromatography (CH2Cl2/MeOH 25:1) gave complex 20
(30 mg, 80%): mp > 300 °C (CH3CN/CH2Cl2). IR (film): 3412,
1660, 1512, 1260, 1159 cm-1. UV-vis (CH2Cl2): λmax 332, 390,
471, 576, 696 nm. MS (ESI): m/z 976.3 (M - Cl)+. Crstal data:
C51H59ClCuFeN11O2; M ) 1012.93; triclinic; P1h; a ) 10.7996-
(15), b ) 15.203(3), c ) 16.414(2) Å; R ) 91.961, â ) 108.348,
UV-vis (CH2Cl2/MeOH 10:1): λmax (log ꢀ) 215 (4.56), 240
(4.66), 335 (4.63), 601 (4.38) nm. MS (FAB): m/z 2064
(M+•). HRMS (MALDI): m/z 2064.9 (M+•). Crystal data:
C112H120Cu2N24O6Zn2‚4C2H5OH; M ) 2340.41; tetragonal; P421c;
a ) 17.2570(17), b ) 17.2570(17), c ) 39.409(4) Å; R ) 90, â )
90, γ ) 90°; V ) 11736(2) Å3; Z ) 4; Dc ) 1.325 g cm-3; µ(Cu
KR) ) 1.418 mm-1; T ) 173(2) K; dark blue blocks; 113 106
reflections collected; F2 refinement; R1 ) 0.1671, w2 ) 0.4492;
8698 observed reflections [|Fo| > 4σ(|Fo|), 2θ ) 143.1°]; 629
parameters.
γ ) 106.412°; V ) 2431.1(6) Å3; Z ) 2; Dc ) 1.384 g cm-3
;
µ(Cu KR) ) 3.854 mm-1; T ) 173(2) K; dark blue needles; 23 912
reflections collected; F2 refinement; R1 ) 0.0706, R2 ) 0.1840;
4943 observed reflections [|Fo| > 4σ(|Fo|), 2θ ) 142.2°]; 618
parameters.
N′,N′,N′′,N′′-Dicopper(II) Di-([7,8,12,13,17,18-hexa-(4-tert-bu-
tylphenyl)-2,3-di-(quinoline-2-carboxamido)porphyrazinato]}-
zinc(II) (18b). DBU (1.9 µL, 0.013 mmol) in DMF (1 mL) was
added to porphyrazine 14b (8.0 mg, 5.3 µmol) in DMF (5 mL).
After 10 min, CuCl2 (1.8 mg, 0.013 mmol) in DMF (1 mL) was
added, and the mixture was stirred for 48 h at ambient tempera-
ture. Rotary evaporation and chromatography (CH2Cl2/MeOH 25:1
and 50:1) gave complex 18b (2.1 mg, 25%): Rf ) 0.18 (CH2Cl2/
Results and Discussion
The masking of peripheral porphyrazinediamino groups
via ring fusion with a selenodiazole residue, first reported
by Ercolani and co-workers,22 has proven to be a flexible
method for the synthesis of a variety of extended por-
phyrazinic systems.17-19,21,22 Using this strategy, the mag-
nesium complexes 1a and 1b and free-base porphyrazines
2a and 2b were synthesized following the procedure of
Baum et al. (Scheme 1).21 The free-base macrocycles were
readily remetalated15 to yield the zinc porphyrazines 3a and
3b (83-85%). Slow evaporation of a methanol, dichlo-
romethane, and pyridine solution of porphyrazine 3a gave
crystals suitable for X-ray structure determination, which
confirmed the composition of the molecule. In the same way,
suitably crystalline porphyrazine 3b was obtained from a
mixed-solvent system. Both crystal structures are given in
the Supporting Information.
MeOH, 25:1). IR (film): 3446, 1735, 1603, 1462, 1371, 987 cm-1
.
UV-vis (CH2Cl2/MeOH 25:1): λmax (log ꢀ) 240 (4.76), 338 (4.33),
630 (4.16) nm. MS (FAB): m/z 3140 (M+•). MS (MALDI): m/z
3140.4 (M+•).
N,O-Copper(II)-[7,8,12,13,17,18-hexapropyl-2-(5-tert-butyl-2-
oxybenzylideneamino)-3-(quinoline-2-carboxamido)porphyrazi-
nato]zinc(II) (19). 5-tert-Butyl-2-hydroxybenzaldehyde (62 µL,
0.65 mmol) was added to porphyrazine 10a (10.6 mg, 0.013 mmol)
and CuCl2 (17 mg, 0.13 mmol) in pyridine (5 mL). After 18 h, the
pyridine was removed by distillation, and the resulting residue was
chromatographed (CH2Cl2/MeOH 10:1) and washed with hexanes
(50 mL) to give salen-porphyrazine 19 (7.6 mg, 56%) as a green-
blue solid: Rf ) 0.42 (MeOH/CH2Cl2 1:10). IR (film): 3384, 1655,
1463, 1156 cm-1. UV-vis (CH2Cl2/MeOH 10:1): λmax (log ꢀ) 251
(4.65), 318 (4.40), 345 (4.41), 608 (4.13), 653 (4.21) nm. MS
(FAB): m/z 1035 (M+•). MS (MALDI): m/z 1036.7 (M+•).
N,O-Copper(II)-[7,8,12,13,17,18-hexapropyl-2-(5-tert-butyl-2-
oxybenzylideneamino)-3-(2-pyridinecarboxamido)porphyrazinato]-
iron(III) chloride (20). 5-tert-Butyl-2-hydroxybenzaldehyde (0.05
mL, 0.3 mmol) was added to porphyrazine 12 (30 mg, 0.030 mmol)
in pyridine (40 mL). After 18 h, the mixture was rotary evap-
orated, and the 16-containing residue and Cu(OTf)2 (110 mg, 0.3
mmol) were dissolved in EtOH and CHCl3 (1:1 40 mL); the mix-
ture was stirred overnight at ambient temperature. Rotary evapora-
Collins and co-workers have developed a series of chelates
from the metal ion complexation by two doubly deprotonated
2-hydroxy-2-methylpropanamide ligands.23-29 The Collins
(23) Christie, J. A.; Collins, T. J.; Krafft, T. E.; Santarsiero, B. D.; Spies,
G. H. J. Chem. Soc., Chem Commun. 1984, 198.
(24) Anson, F. C.; Christie, J. A.; Collins, T. J.; Coots, R. J.; Furutani, T.
T.; Gipson, S. L.; Keech, J. T.; Krafft, T. E.; Santarsiero, B. D.; Spies,
G. H. J. Am. Chem. Soc. 1984, 106, 4460.
(25) Collins, T. J.; Coots, R. J.; Furutani, T. T.; Keech, J. T.; Peake, G. T.;
Santarsiero, B. D. J. Am. Chem. Soc. 1986, 108, 5333.
(26) Collins, T. J.; Slebodnick, C.; Uffelman, E. S. Inorg. Chem. 1990,
29, 3433.
Inorganic Chemistry, Vol. 45, No. 9, 2006 3689

Goslinski et al.
Scheme 2 a
Table 1. Selected Bond Lengths (Å) and Angles (deg) for 14a‚2py
Zn-N(7)
Zn-N(12)
Zn-N(63)
2.0023(19)
1.9981(18)
2.137(2)
Zn-N(2)
Zn-N(17)
2.0069(18)
2.0099(19)
N(2)-Zn-N(7)
N(2)-Zn-N(17)
N(7)-Zn-N(12)
N(7)-Zn-N(63)
N(12)-Zn-N(63)
86.69(7)
87.31(7)
87.78(8)
99.71(8)
104.53(8)
N(2)-Zn-N(12)
N(2)-Zn-N(63)
N(7)-Zn-N(17)
N(12)-Zn-N(17)
N(17)-Zn-N(63)
154.23(8)
101.21(8)
154.95(8)
87.13(7)
105.31(8)
chelates have two unique features that make them of
considerable value in the development of novel magnetic
materials. Most notable is their redox stability, which makes
the ligands capable of stabilizing unusual high-valent transi-
tion metal ions such as cobalt(IV),30,31 iron(IV),32,33 and
manganese(V)28,34 and also allowing access to M1-M2
complexes with the metals at different valencies and spin
states. We sought to append the Collins ligands to a
porphyrazine since this may allow for the complexation of
paramagnetic cations with peripherally functionalized, an-
ionic porphyrazines, to prepare magnetically ordered charge-
transfer salts, as have been reported for “simple” Collins
complexes.35
Reaction of the free porphyrazinediamine 4a, generated
in situ from the reductive cleavage of selenodiazole 1a using
hydrogen sulfide, with excess 2-acetoxy-2-methylpropanoyl
chloride and acidic workup gave porphyrazine 6 (65%). This
macrocycle was immediately metalated with zinc(II) acetate
to give complex 7 (94%) and saponified to provide por-
phyrazine 8 (80%) (Scheme 1). Slow evaporation of a DMSO
solution of porphyrazine 8 yielded crystals suitable for an
X-ray structure determination (Table 1). The Zn ion was
coordinated to the porphyrazine core with a DMSO molecule
in its apical position. Two Collins ligands are linked to the
pz macrocycle through amide bonds whose C-N bond
lengths (1.353(5) and 1.362(5) Å) are comparable to reported
values by Collins (1.352(7) and 1.367(7) Å, respectively).34
The carbonyl groups have a trans geometry with the N-H
groups to alleviate the steric interaction. Unfortunately,
attempted complexation of a variety of metal ions [Cu(II),
Ni(II), Co(III)] at the peripheral â-hydroxy-amide ligands
in porphyrazine 8 by deprotonation using diverse bases
(NaOH, NaOMe, t-BuOK, (i-Pr)2NLi, t-BuLi, or Et3N) and
reaction with metal salts gave only intractable mixtures of
unstable metal complexes.
a Reagents and conditions: (a) MeO2CCOCl or quinoline-2-COCl,
pyridine, 20 °C, 4-18 h (5-44%); (b) FeBr2, 2,6-lutidine, THF, PhMe, ∆,
20 h; 1 M HCl (40%); (c) pyridne-2-COCl.HCl, pyridine, 20 °C, 18 h; 1 M
HCl; (d) or 2-HO-5-t-BuC6H3CHO, pyridine, 18 h. *Both 16 and 17 were
directly converted into 20 and 19 respectively, see Scheme 4.
As a consequence, we sought to prepare porphyrazines
functionalized with alternative chelating functionalities,
including peripheral oxamido, 2-quinolinecarboxamido, and
2-pyridinecarboxamido groups, by amine acylation (Scheme
2). During these studies it was discovered that the two amino
groups in diamines 4b, 5a, and 5b underwent reaction with
electrophiles at significantly different rates. In many cases,
prolonged reaction of porphyrazinediamines 4b, 5a, or 5b
with an acylating reagent resulted in the formation of
mixtures of mono- and diacylated products. Attempted
diacylation using vast excesses of an acyl chloride did not
drive the reaction to completion but resulted in extensive
decomposition. It was found to be preferable to first isolate
monoamides 9, 10a, and 10b and to, subsequently, carry out
the second acylation in a separate operation. Such transfor-
(27) Collins, T. J.; Kostka, K. L.; Uffelman, E. S.; Weinberger, T. L. Inorg.
Chem. 1991, 30, 4204.
(28) Workman, J. M.; Powell, R. D.; Procyk, A. D.; Collins, T. J.; Bocian,
D. F. Inorg. Chem. 1992, 31, 1548.
(29) Sen Gupta, S.; Stadler, M.; Noser, C. A.; Ghosh, A.; Steinhoff, B.;
Lenoir, D.; Horwitz, C. P.; Schramm, K.-W.; Collins, T. J. Science
2002, 296, 326.
(30) Anson, F. C.; Collins, T. J.; Coots, R. J.; Gipson, S. L.; Richmond, T.
G. J. Am. Chem. Soc. 1984, 106, 5037.
(31) Collins, T. J.; Powell, R. D.; Slebodnick, C.; Uffelman, E. S. J. Am.
Chem. Soc. 1991, 113, 8419.
(32) Collins, T. J.; Kostka, K. L.; Munck, E.; Uffelman, E. S. J. Am. Chem.
Soc. 1990, 112, 5637.
(33) Kostka, K. L.; Fox, B. G.; Hendrich, M. P.; Collins, T. J.; Rickard,
C. E.; Wright, L. J.; Mnck, E. J. Am. Chem. Soc. 1993, 115, 6746.
(34) Collins, T. J.; Gordon-Wylie, S. W. J. Am. Chem. Soc. 1989, 111,
4511.
(35) Eichhorn, D. M.; Telser, J.; Stern, C. L.; Hoffman, B. M. Inorg. Chem.
1994, 33, 3533.
3690 Inorganic Chemistry, Vol. 45, No. 9, 2006

Porphyrazines as Molecular Scaffolds
Scheme 3 a
a Reagents and conditions: (a) CuCl2, DBU, DMF 20 °C, 24-48 h
(25-37%).
Figure 1. Molecular structure of porphyrazine 8 (50% probability
ellipsoids).
1.9981(18) and 2.0099(19) Å, Table 1], lying ca. 0.44 Å
out of the {N(2),N(7),N(12),N(17)} plane which is coplanar
to better than 0.01 Å. Not surprisingly, the Zn-N bond to
the coordinated pyridine molecule [2.137(2) Å] is signifi-
cantly longer than those to the porphyrazine nitrogens. The
porphyrazine ring has a slightly dished conformation; the
outer four nitrogens are coplanar to within ca. 0.01 Å, and
although the inner and outer N4 planes are parallel (inclined
by less than 1°), they have a mean interplanar separation of
ca. 0.11 Å such that the metal lies ca. 0.55 Å out of the
outer {N(1),N(6),N(11),N(16)} plane (cf., ca. 0.44 Å for the
inner N4 plane). The two quinolinecarboxamido moieties
have noticeably different conformations as a consequence
of the intramolecular N-H‚‚‚O hydrogen bond between them
(Figure 2a). For the N(21)/N(24) moiety, the amide and
quinoline units are inclined by ca. 10° and the amide is
inclined by ca. 28° to its parent pyrrole ring, while for the
N(33)/N(36) unit the corresponding twists are ca. 4 and 53°.
It is noticeable that in each quinolinecarboxamido group the
amide N-H is positioned proximal to the quinoline nitrogen,
suggesting some N-H‚‚‚N interaction; the N(21)-H‚‚‚N(24)
and N(33)-H‚‚‚N(36) N‚‚‚H separations are ca. 2.19 and
2.23 Å, respectively. The crystal structure of the related zinc-
porphyrazine diamide complex, 14b, was also determined
(see Supporting Information). The di-(2-quinolinecarbox-
amido)-porphyrazines, 14a and 14b, are structurally related
to the known di-(2-picolinamido)-porphyrazines,2 but they
have greater stability and solubility and, therefore, are more
readily synthesized and derivatized.
Figure 2. Molecular structure of 14a‚2py. The N-H‚‚‚O hydrogen bond
(a) has N‚‚‚O ) 2.836(3) Å, H‚‚‚O ) 2.13 Å, and N-H‚‚‚O ) 135°.
mations were less than ideal for the synthesis of symmetrical
diamides 13, 14a, and 14b but have proven to be immensely
valuable for the synthesis of mixed-ligand systems, vide infra.
Although monoamides 9, 10a, and 10b were less unstable
than the corresponding monoimino derivatives with 5-tert-
butyl-2-hydroxybenzaldehyde,17 slow aerobic decomposition
was still observed, and monoamides 9, 10a, and 10b were
immediately used in subsequent steps. The amino-amide 11,2
prepared from porphyrazine 2a via monoacylation of the
derived diamine 4b with 2-picolinyl chloride, was converted
by metalation using iron(II) bromide and subsequent oxida-
tion into the derived Fe(III) complex 12. Although selective
macrocycle metalation was possible in the presence of the
amino-amide unit, the reaction proceeded with only a modest
yield (40%).
During the preparation of diamides 14a and 14b, partial
demetalation was observed, thereby giving access to free base
macrocycles 15a and 15b. Slow evaporation of methanol/
dichloromethane/pyridine solutions of diamide 14a gave
crystals suitable for X-ray structure determination. The solid-
state structure of 14a has been determined as both the
nonsolvated (14a, see Figure S1 in the Supporting Informa-
tion) and pyridine solvated (14a‚2py, Figure 2) forms.
(Note: both forms have a metal-coordinated pyridine mol-
ecule.) Since the nonsolvated version has some disorder in
the porphyrazine ring (see Figure S2), the discussion will
concentrate on the pyridine solvate. The five-coordinate
square-based pyramidal zinc center perches almost sym-
metrically on top of the inner four nitrogens of the por-
phyrazine ring [the four Zn-N(pz) distances range between
Reaction of oxamido-porphyrazine 13 with copper(II)
chloride and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) gave
a violet copper complex in moderate yield (19-52%).
Unfortunately, this was unstable and not amenable to full
characterization. Attempted metalation with nickel(II), zinc-
(II), or platinum(II) also gave unstable complexes, which
were not characterized further. In contrast, reaction of the
di-(2-quinolinecarboxamido)-porphyrazines, 14a and 14b,
with copper(II) chloride and DBU gave the complexes 18a
and 18b (Scheme 3). The crystal structure36 of the mixed-
(36) The quality of the data set is somewhat poor, and consequently, a
number of areas of the structure (such as the quinoline moieties) had
to be optimized and thus the metrical parameters must be treated with
some caution. The overall topology of the structure, however, is beyond
question.
Inorganic Chemistry, Vol. 45, No. 9, 2006 3691

Goslinski et al.
ecarboxamido moieties somewhat uncertain, but despite this,
it is clear that, as in both 14a and 14a‚2py, the amide and
quinoline units are approximately coplanar (inclined by ca.
3 and 8° for the N(21)/N(24) and N(33)/N(36) units,
respectively) and that the quinolinecarboxamido moieties are
steeply inclined to their parent pyrrole rings. However,
whereas in 14a and 14a‚2py the inclinations of the two
quinolinecarboxamido were very different (ca. 23 and 61°
in 14a and ca. 28 and 53° in 14a‚2py), in 18a they are
much more similar (ca. 50 and 42° for the N(21)/N(24) and
N(33)/N(36) units, respectively). This is no doubt a conse-
quence of the coordination to the bridging copper centers.
The geometry at the copper centers is markedly distorted
tetrahedral, the {Cu,N(21A),N(24A)} and {Cu,N(33),N(36)}
planes being twisted so that there is an angle of ca. 51°
between them (cf. 90° in ideal tetrahedron coordination)
(Table 2). This structure is very similar to its closely related
2-picolinamide analogue2 with peripheral copper centers
linking the two porphyrazine rings. However, in the literature
structure (which has molecular rather than crystallographic
C2 symmetry), the nickel centers linked to the porphyrazine
rings lie within the plane of the inner four nitrogen atoms
unlike the zinc centers here in 18a which perch “above” them
(vide supra).
The availability of either complex, 18a or 18b, with
peripheral propyl or 4-tert-butylphenyl substituents highlights
the flexibility of the synthesis and allows the opportunity to
fine-tune the physical properties, such as solubility, of these
novel tetrametallic complexes.15 As for the di-(2-picolin-
amido) analogues, we found dicopper complex 18a to be
EPR silent, an observation which leads to the conclusion
that the two spins at the periphery of the dimer are strongly
antiferromagnetically coupled, with a diamagnetic S ) 0
ground state and negligible thermal population of the
corresponding triplet excited state.2
Figure 3. Molecular structure of the C2-symmetric complex 18a. The C2
axis is in the plane of the paper and bisects the Zn‚‚‚ZnA and Cu‚‚‚CuA
vectors; the Zn‚‚‚ZnA and Cu‚‚‚CuA separations are 4.548(3) and
4.403(3) Å respectively.
Table 2. Selected Bond Lengths (Å) and Angles (deg) for 18a
Zn-N(2)
1.977(7)
1.947(8)
2.132(8)
2.036(4)
1.934(5)
Zn-N(7)
1.959(10)
2.033(11)
2.029(8)
Zn-N(12)
Zn-O(63)
Cu-N(36)
Cu-N(24A)
Zn-N(17)
Cu-N(33)
Cu-N(21A)
2.005(14)
N(2)-Zn-N(7)
90.0(4)
88.7(4)
86.2(5)
106.1(4)
100.8(5)
81.2(3)
152.2(4)
105.6(2)
N(2)-Zn-N(12)
N(2)-Zn-O(63)
N(7)-Zn-N(17)
N(12)-Zn-N(17)
N(17)-Zn-O(63)
N(33)-Cu-N(21A)
N(36)-Cu-N(21A)
N(21A)-Cu-N(24A)
165.6(5)
93.6(4)
161.1(5)
90.3(4)
92.8(6)
108.0(5)
142.1(4)
83.3(4)
N(2)-Zn-N(17)
N(7)-Zn-N(12)
N(7)-Zn-O(63)
N(12)-Zn-O(63)
N(33)-Cu-N(36)
N(33)-Cu-N(24A)
N(36)-Cu-N(24A)
metal zinc-copper diamide 18a showed the complex to be
a C2-symmetric back-to-back porphyrazine dimer linked by
a pair of copper centers that each coordinate to a quinolin-
ecarboxamido moiety from both the “upper” and “lower”
porphyrazines (Figure 3). The N8 “planes” (vide infra) of
the two porphyrazine rings are offset such that their centroid‚
‚‚centroid separation is ca. 4.04 Å compared to a mean
interplanar separation of ca. 3.32 Å; the two planes are
inclined by ca. 8°. The geometry at the zinc center is the
expected square-based pyramidal, although compared to 14a
and 14a‚2py the metal sits closer (ca. 0.29 Å compared to
0.47 and 0.44 Å in 14a and 14a‚2py, respectively) to the
plane of the inner four nitrogens (which are coplanar to
within ca. 0.04 Å). Associated with this, three of the four
Zn-N(pz) coordination distances are shorter than those seen
in 14a and 14a‚2py, although, for some reason, that to N(17)
is longer (Table 2). In contrast to the dished conformations
seen for 14a and 14a‚2py, the porphyrazine ring in 18a has
a slightly twisted conformation, N(6) and N(12) lying ca.
0.15 and -0.12 Å out of and on opposite sides of the
{N(1),N(2),N(7),N(11),N(16),N(17)} plane which is coplanar
to within ca. 0.03 Å. The optimization of the quinoline rings36
renders detailed analysis of the orientation of the quinolin-
The UV-vis spectra of dimers 18a and 18b exhibit intense
Soret bands at λmax ) 335 and 338 nm and Q-bands at λmax
) 601 and 630 nm, respectively. Alternatively, the precursor
macrocycles, 14a and 14b, display intense Soret bands at
λmax ) 350 and 374 nm and Q-bands at λmax ) 616 and 641
nm, respectively. Therefore, by comparison, formation of the
copper(II)-linked porphyrazine dimer results in a blue shift
of 15 nm for the Soret band of 18a and a blue shift of 36
nm for 18b. As reported for our di-(picolinamido) porphyra-
zine dimer,2 porphyrin sandwich complexes, and cofacial
porphyrin complexes, this blue shift is a result of π-π
interactions between adjacent macrocycles.37,38 The magni-
tude of the shift is impressive however, especially for the
4-tert-butylphenyl analogue 18b, since previously, shifts of
approximately 9 nm have been reported. This curious result
is the subject of further study.
Significant donation of electron density from the peripheral
amino groups into the macrocyclic ring system has been
demonstrated previously by cyclic voltammetry.15 Conse-
(37) Bilsel, O.; Rodriguez, J.; Milam, S. N.; Gorlin, P. A.; Girolami, G.
S.; Suslick, K. S.; Holten, D. J. Am. Chem. Soc. 1992, 114, 6528.
(38) Collman, J. P.; Kendall, J. L.; Chen, J. L.; Eberspacher, T. A.; Moylan,
C. R. Inorg. Chem. 1997, 36, 5603.
3692 Inorganic Chemistry, Vol. 45, No. 9, 2006

Porphyrazines as Molecular Scaffolds
Table 3. Electrochemical Study of Dimer 18aa
Figure 4. Molecular structure of 20.
Table 4. Selected Bond Lengths (Å) and Angles (deg) for 20
Fe-Cl
2.3259(15)
1.920(4)
1.921(4)
1.866(4)
1.982(5)
Fe-N(2)
1.941(4)
1.933(4)
1.961(4)
1.927(4)
pz2+/pz+
pz+/pz
pz/pz1-
pz1-/pz2-
Fe-N(7)
Fe-N(17)
Cu-O(27)
Cu-N(39)
Fe-N(12)
Cu-N(21)
Cu-N(32)
18a
0.365 (118)
-0.001 (82)
-1.035 (94)
-1.297 (146)
a Figure shows the conversion of half-wave potentials (V vs Fc+/Fc,
measured in dichloromethane, with 0.1 M Bu4NPF6 as electrolyte, Pt disk
working electrode, and at a scan rate of 110 mVs-1) and E- (∆Ep, mV).
Cl-Fe-N(2)
Cl-Fe-N(12)
99.43(14)
97.84(14)
88.96(17)
88.87(17)
161.14(19)
94.63(17)
167.71(17)
96.68(18)
Cl-Fe-N(7)
Cl-Fe-N(17)
97.48(14)
101.36(14)
162.72(19)
88.39(19)
88.14(19)
86.34(17)
177.87(18)
82.52(17)
Scheme 4 a
N(2)-Fe-N(7)
N(2)-Fe-N(17)
N(7)-Fe-N(17)
N(21)-Cu-O(27)
N(21)-Cu-N(39)
O(27)-Cu-N(39)
N(2)-Fe-N(12)
N(7)-Fe-N(12)
N(12)-Fe-N(17)
N(21)-Cu-N(32)
O(27)-Cu-N(32)
N(32)-Cu-N(39)
a solution of complex 20 in dichloromethane gave crystals
suitable for X-ray analysis. As was seen for the zinc
complexes 14a, 14a‚2py, and 18a, the metal here in complex
20 (Figure 4) again adopts a square-based pyramidal
geometry, perching ca. 0.30 Å above the porphyrazine N8
plane; the Fe-N distances are in the range of 1.920(4)-
1.941(4) Å. The coordination plane around the distorted
square planar copper center is only slightly inclined to this
plane (ca. 5°), even though the pyridine nitrogen N(39) lies
ca. 0.21 Å out of the {Cu,N(21),O(27),N(32)} plane which
is coplanar to within ca. 0.02 Å; the copper lies ca. 0.27 Å
out of the N8 plane. When the N(39) center is omitted, the
{CuN2O} plane is inclined by ca. 3° to the N8 plane. The
picolinamide moiety has a near planar conformation, the
amide and pyridyl groups being inclined by only ca. 2°, but
the picolinamide as a whole is slightly inclined with respect
to its parent pyrrole ring (ca. 7°), thus moving N(39) out of
the {CuN2O} plane (Table 4). As is seen here in complex
20, in the closest related literature structure (µ2-2,3,12,13,-
17,18-hexapropyl-7,8-bis((5-tert-butyl-2-oxybenzylidene)-
imino))-chloro-copper-manganese(III),17 the porphyrazine
ring is planar (to within better than 0.01 Å) with the
manganese perching on top of the inner N4 atoms (by ca.
0.31 Å). In contrast to the out-of-plane distortion seen for
the pyridyl nitrogen N(39) here in complex 20 (vide supra),
in the literature structure,17 the copper coordination sphere
is symmetric (two salicylaldimine moieties cf. one salicyl-
a Reagents and conditions: (a) CuCl2 or Cu(OSO2CF3)2, pyridine, 20
°C, 18 h (56%, 80%).
quently, these porphyrazines are more easily oxidized than
the analogous phthalocyanines and porphyrins. However,
substitution of an amino group by an electronically with-
drawing acetyl or trifluoroacetyl group results in an in-
crease in the oxidation potential of the resulting porphyra-
zines, which leads to a macrocycle which is more difficult
to oxidize.39 Indeed, the first and second oxidation poten-
tials of 18a are -0.001 and 0.365 V, indicating the dimer
macrocycles are 130 mV more difficult to oxidize than 2H-
[Pz((NMe2)2Pr6)] (Table 3). In addition, dimer 18a exhibits
reduction potentials of -1.035 V and -1.297 V. The results
mirror those obtained for our di-(picolinamido) porphyrazine
dimer.2
Since the synthetic strategy employed for the majority of
the derivatives involves a transient monosubstituted species,
the possibility of synthesizing unsymmetrical mixed-ligand
systems was explored. Toward this end, porphyrazines 10a
and 12 were allowed to react with 5-tert-butyl-2-hydroxy-
benzaldehyde, followed by copper(II) chloride or triflate and
pyridine. This gave the bimetallic complexes 19 (56%) and
20 (80%) (Scheme 4). Recently, we have applied this same
synthetic method for the synthesis of related complexes, 20
(M ) VO, MnCl, Cu).40 Slow diffusion of acetonitrile into
(39) Fuchter, M. J.; Vesper, B. J.; Murphy, K. A.; Collins, H. A.; Philips,
D.; Hoffman, B. M.; Barrett, A. G. M. J. Org. Chem. 2005, 70, 2793.
(40) Zhong, C.; Zhao, M.; Goslinski, T.; Stern, C.; Barrett, A. G. M.;
Hoffman, B. M. Inorg. Chem. 2006, submitted for publication.
Inorganic Chemistry, Vol. 45, No. 9, 2006 3693

Goslinski et al.
aldimine and one picolinamide unit in 20) and coplanar to
within ca. 0.06 Å.
In the EPR spectrum of porphyrazine 20, spin coupling
between the Fe(III) and Cu(II) center is observable, but the
exact nature of this coupling is complex. The UV-vis
or using 5-tert-butyl-2-hydroxybenzaldehyde. The resultant
polydentate ligands were converted into bimetallic complexes
and tetrametallic porphyrazine dimer complexes. Extension
of this work to the synthesis of alternative molecular scaffolds
and the development of novel magnetic and electronic
materials will be reported in due course.
spectrum of 20 is also complex with absorbances at λmax
)
332, 390, 471, 576, and 696 nm. In addition to the B- and
Q-bands observable for porphyrazines,15 Fe(III) tetraazapor-
phyrin complexes of intermediate spin exhibit intense charge-
transfer bands in the near-UV and near-IR regions (at
approximately 400-450 and 650-725 nm).41 It is therefore
plausible that the bands at 471 and 696 nm arise from charge-
transfer bands between the macrocyclic ligand or the axial
ligand and the Fe(III) center.
Acknowledgment. We thank GlaxoSmithKline for the
generous endowment (to A.G.M.B), the Royal Society and
the Wolfson Foundation for a Royal Society Wolfson
Research Merit Award (to A.G.M.B.), the Wolfson Founda-
tion for establishing the Wolfson Centre for Organic
Chemistry in Medical Sciences at Imperial College, the
Engineering and Physical Sciences Research Council, the
National Science Foundation, and the European Commission
for a Marie Curie Fellowship (to T.G.) in support of our
studies.
Conclusions
Several porphyrazinediamines were converted into mono-
acyl, diacyl, and acyl-imine derivatives using the acid
chlorides from 2-picolinic acid or 2-quinolinecarboxylic acid
Supporting Information Available: General experimental
procedures and structural data with CIF files for all new compounds.
This material is available free of charge via the Internet at
http://pubs.acs.org.
(41) Stuzhin, P. A.; Hamdush, M.; Ziener, U. Inorg. Chim. Acta 1995, 326,
131.
IC060176N
3694 Inorganic Chemistry, Vol. 45, No. 9, 2006