Spectroscopic studies of novel porphyrin-copper(II) and zinc(II) complexes that share the pinch-porphyrin family structure of iron(III) complex models of peroxidases |
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Authors: | Gárate-Morales José Luis Reyes-Ortega Yasmi Alvarez-Toledano Cecilio Gutiérrez-Pérez René Ramírez-Rosales Daniel Zamorano-Ulloa Rafael Basurto-Uribe Eduardo Hernández-Díaz Julio Contreras Rosalinda |
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Institution: | (1) Centro de Química, Instituto de Ciencias, Universidad Autónoma de Puebla, 14 Sur 6301. Col. San Manuel. Puebla, Pue, 72570, México;(2) Instituto de Química, Universidad Nacional Autónoma de México, Circuito exterior S/N, Ciudad Universitaria, México, D.F, 04510, México;(3) Facultad de Ciencias Químicas, Universidad Autónoma de Puebla, Ave. San Claudio S/N, Ciudad Universitaria. Puebla, Pue, 72570, México;(4) Escuela Superior de Física y Matemáticas, Instituto Politécnico Nacional, Ave Instituto Politécnico Nacional S/N, Edif. 9, Unidad Profesional Adolfo López Mateos, San Pedro Zacatenco, México, D.F, 07738, México;(5) Departamento de Ciencias Básicas, Universidad Autónoma Metropolitana-Azcapotzalco, Ave San Pablo 180, México, D.F, 02200, México;(6) Departamento de Química, Centro de Investigaciones y de Estudios Avanzados del IPN, A.P. 14-740, México, D.F, 07000, México |
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Abstract: | Six novel pinch-porphyrin complexes (picdien)(protoporphyrinate dimethyl ester)]copper(II) (7), (picdien)(mesoporphyrinate dimethyl ester)]copper(II) (8) and (picdien)(deuteroporphyrinate dimethyl ester)]copper(II) (9), (picdien)(protoporphyrinate dimethyl ester)]zinc(II) (13), (picdien)(mesoporphyrinate dimethyl ester)]zinc(II) (14) and (picdien)(deuteroporphyrinate dimethyl ester)]zinc(II) (15), were prepared from the corresponding free copper(II)-porphyrins (4–6), and zinc(II)-porphyrins (10–12) and picdien (N-(3H-imidazol-4-ylmethyl)-N-{2-(3H-imidazol-4-ylmethyl)-amino]-ethyl}-ethane-2,3-diamine). Spectroscopic studies show that complexes (7–9) and (13–15) have the pinch-porphyrin type structure previously found in iron(III) complex models of peroxidases. Complexes (7–9), were characterized by u.v.–vis., m.c.d., and e.s.r. spectroscopy. E.s.r. spectra of the copper parent compounds (4–6) at ca. 10–2–10–4 M concentrations were typical of copper(II)-dimers. The addition of the picdien ligand broke up the dimers as detected by e.s.r. Compounds (7–9) are predominantly monomeric at ca. 10–3 M concentration. The presence of picdien in (7–9) distorts the porphyrin internal portion of the plane so as to make these four internal nitrogen atoms, coordinated to copper(II), e.s.r.-distinguishable. MO and ligand field theories were used to characterize and to evaluate the directional covalence parameters of compounds (7–9). A non-fully axial, out-of-the-porphyrin-plane bonding was found for (7–9), similar to the bonding of the pinch-porphyrins-iron(III). However the in-plane distortion produced by the presence of the picdien ligand on copper(II) is significantly larger than in pinch-porphyrin-iron(III). The n.m.r. data show that the porphyrin-zinc(II) is the less strained and has the weakest bonded structure. The coordination number of the pinch-porphyrin with iron(III), copper(II) and zinc(II), is in all cases six. |
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