Phthalocyanines and related complexes are important compounds due to their special electrical and optical properties. This article describes, after a more preparative part on the synthesis of porphyrins and phthalocyanines, the different ways to use the macrocycles for the mentioned properties.

https://link.springer.com/content/pdf/10.1007%2F3-540-52899-7_2.pdf

Phthalocyaninatometal and related complexes with special electrical and optical properties

Tetraazaporphyrins (TAPs), phthalocyanines (Pcs), naphthalocyanines (Ncs), and anthracocyanines (Acs) with four tert-butyl groups attached at similar positions have been synthesized, and their electronic absorption, magnetic circular dichroism (MCD), IR, and voltammetric properties were studied and interpreted with the help of quantum-mechanical calculations. Through the preparation of a series of compounds with the same number of the same substituent, the effects of the increase in the size of the ring system were clearly derived. The main results may be summarized as follows. 1) The Q band shifts to longer wavelength and its intensity increases, but with decreasing degree of change with increasing molecular size. If the size of the effect of benzene directly fused to the TAP skeleton is set at unity, the effects of the second and third benzene units are roughly 0.8 and 0.5, respectively. 2) The splitting of the Q bands in metal-free compounds decreases with increasing molecular size, so that the Q bands of H2Nc and H2Ac appear as single bands. 3) The magnitude of the orbital angular momentum of the excited state of the ligand decreases with increasing molecular size. 4) Interestingly, the ring current, as judged from the positions of pyrrole proton signals in the 1H NMR spectrum, appears to decrease with increasing molecular size. 5) The first reduction potential becomes less negative, but only slightly, whereas the first oxidation potential shows a marked shift to less positive values with increasing molecular size, indicating that the HOMO destabilizes significantly as the molecule becomes larger. 6) In 5), the extent of the HOMO destabilization with molecular size differs depending on the central metal, so metals producing smaller destabilization effects can allow larger macrocycles. Of the metals studied, the most effective is cobalt, and the practical size limit is represented by the Acs. 7) The IR spectra become simpler the larger the molecule, and the main bands were assigned by DFT calculations. 8) The trend in experimentally determined redox potentials and electronic absorption and MCD spectra were reasonably reproduced by MO calculations using the ZINDO/S Hamiltonian. 9) EPR data for several metallocomplexes are also reported.

Synthesis, spectroscopy, and electrochemistry of tetra-tert-butylated tetraazaporphyrins, phthalocyanines, naphthalocyanines, and anthracocyanines, together with molecular orbital calculations.

Macrocyclic copper(II) complexes: Superoxide scavenging activity, structural studies and cytotoxicity evaluation

μ-Carbido diporphyrinates and diphthalocyaninates of general formula [{Mp2−}2(μ-C)] (p2− = tpp (M = Fe), oep (Fe), pc (Fe, Ru); H2tpp: 21H,23H-5,10,15,20-tetraphenylporphine; H2oep: 21H,23H-2,3,4,8,12,13,17,18-octaethylporphine; H2pc: 29H,31H-phthalocyanine) of formally FeIV and RuIV are prepared by a new and improved ‘one-pot’ synthesis. The corresponding chloro complexes of the tervalent metal ions react successively with potassium hydroxide in boiling 2-propanol and then with trichloromethane. Potassium hydroxide is proven to be a very versatile and powerful reductant in tetrapyrrolic chemistry. As evidenced from electron spin resonance and UV vis spectral measurements, the precursor is reduced primarily to an ate-complex of type [MIp2−]− of a formally monovalent metal ion. This active species is assumed to react with trichloromethane via a dichlorocarbene complex of type [MII(CCl2)p2−] to yield the actual -carbido complex. [{Feoep2−}2(μ-C)] is crystallographically characterized. It is monoclinic, space group C12/c1 (15), with a = 18.279(3) A, b = 15.005(2) A, c = 23.392(7) A, β = 107.12(2)°, Z = 4, R1 = 0.0773. The iron atom is displaced by 0.192(3) A out of the centre (Ct) of the (Np)4 plane toward the (μ-C) atom. Average d(Fe-Np) is 1.986(5) A; d(Fe-(μ-C)) is 1.6638(9) A. The Fe-C-Fe skeleton is linear (179.5(3)°). The two slightly waving porphyrinato cores are in a staggered conformation, the (Np-Fe-Fe″-Np″) torsion angle being 21.0(3)°. Solutions of each μ-carbido complex in pyridine/dichloromethane show four distinct quasi-reversible redox processes in their differential-pulse voltammograms and these are assigned to the successive one-electron reduction and oxidation of the macrocyclic ligands. 13C CP MAS NMR spectra indicate effective four-fold symmetry within the series of the μ-carbido complexes with isotropic shifts occurring at similar fields to those of the corresponding macrocyclic complex of a closed-shell metal ion. Resonances of the bridging carbon atom are not detected. A characteristic increase of line broadening within the series tpp2− > oep2− > pc2− may be due to Fermi contact interactions with the strongly coupled low-spin MIV centres. The magnetic susceptibility studies show that the complexes all display non-zero μ values at 295 K increasing from pc2− to tpp2−. Mossbauer spectra confirm the low-spin FeIV oxidation state for the iron centres. Isomer shift, δ, and quadrupole splitting, ΔEQ, for [{Fepc2−}2(μ-C)] and [{Fetpp2−}2(μ-C)] are identical to those previously reported. Data for [{Feoep2−}2(μ-C)] are essentially the same as for the pc and tpp complex. Thus the order of δ is tpp ≈ oep > pc whilst that of ΔEQ is pc >> oep > tpp. Small impurity lines are observed which help explain the magnetic data. UV vis/NIR spectra of the μ-carbido complexes show the characteristic π-π* transitions. These are shifted with respect to the corresponding mononuclear complexes to higher energy because of excitonic interactions. Vibrational spectra are discussed in detail νas(M-C-M) (in cm−1) is at 937 (M = Fe; tpp) ν > 25 000 cm−1.

W.C. Lin

Papers

Electron spin resonance and electronic structure of some metalloporphyrins