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.

Two terbium ions in a triple-decker complex (Pc)Tb(Pc)Tb(T(p-OMe)PP) (Pc = phthalocyaninato, T(p-OMe)PP = tetra-p-methoxyphenylporphyrinato) have shown sharply different magnetic behaviours depending on symmetry of the coordination polyhedron. The fast quantum tunnelling relaxation process in a square-prismatic site has been revealed to be hindered by magnetic-dipolar coupling between the f-electronic systems.

Blazing saddles: A supramolecular conglomerate is formed by intermolecular hydrogen bonding between two saddle‐distorted ZnII–phthalocyanine complexes coordinated by 4‐pyridinecarboxylate and one doubly protonated saddle‐distorted porphyrin dication. The assembly undergoes photoinduced intrasupramolecular electron transfer to generate an electron‐transfer state with the lifetime of 667 ps.

Most of the applications of phthalocyanines (Pcs) are concerned with the large, flat π-conjugation system, as well as the type of central metal. 1 In particular, it is well-known that, compared with porphyrins, 2 the metalloPcs (MtPcs) have extremely high planarity: for example, nonsubstituted NiPc is essentially perfectly planar, 3 although MtPcs with larger metal ions such as Pb and Sn distort the geometry to some extent. 4 Structurally distorted Pcs have been reported in the past few years, where the steric congestion of substituents caused distortion of the macrocycle. 4,5 In this communication, we report two types of Pc analogues whose nonplanarity appears to be the highest yet reported. To induce the largest distortion conceivable, aromatic ortho-dinitriles having two protruding phenyl groups, 3 and 4, are used. These types of dinitriles have long been believed to be too congested to form Pcs by themselves 6 and have therefore been employed for the preparation of opposite type of MtPc analogues, utilyzing the steric hindrance between the phenyl groups. 7 In the course of studies, however, we thought that, if these dinitriles can occupy the adjacent positions of Pcs, the deviation from planarity would be very large because of the overlap of the protruding phenyl groups. 8 As described below, we have overcome this problem, and the resultant two Pc analogues obtained by the above inverse concept, 1 and 2, are indeed confirmed to be the most nonplanar Pcs ever substantiated structurally.Both 1 9 and 2 10 were prepared by the so-called lithium method 1 at ca. 170 and 150 °C, respectively (Scheme 1). In the case of 2, dinitriles 4 and 5 were co-macrocyclized, so that repeated chromatography was inevitably required. They were characterized using mass spectra, elemental analysis, and 1 H NMR (only for 1) 9,10 and their molecular structures were analyzed by X-ray crystallography. Crystals were grown in either chloroform-hexane (1) or acetone-containing toluene (2).

Benzene- or 2,3-naphthalene-ring-expanded tetraazachlorins (TACs), tetraazabacteriochlorins (TABCs), and tetraazaisobacteriochlorins (TAiBCs) have been synthesized by using tetramethylsuccinonitrile as a source of hydrogenated sites. The derived compounds were characterized by using NMR spectroscopy, X-ray crystallography, electronic and magnetic circular dichroism (MCD) spectroscopy, and electrochemical and spectroelectrochemical methods. X-ray analysis revealed that the benzene-fused TAiBC deviates slightly from planarity at the hydrogenated sites as a result of the presence of sp(3) carbons, which prefer a nonplanar tetrahedral conformation. The spectral data were analyzed by using a band deconvolution technique. In the electronic absorption spectra of TAC and TABC species, the Q band splits into two intense components and smaller splittings were observed for the 2,3-naphthalene-fused derivatives relative to the benzo-fused species. In contrast, in the case of TAiBCs, the Q band splitting was apparently not observed in absorption spectra, as expected from the C(2v) molecular symmetry. However, MCD signals of the Q band in TAiBCs showed Faraday B terms, implying that the accidental degeneracy of the LUMO and LUMO+1 was broken even for adjacently ring-fused species. Relative molecular orbital energies were estimated by using cyclic and differential pulse voltammetry. The first reduction potentials were close for TACs and TABCs, although those of TAiBCs shifted to more negative potentials. In contrast, although TABCs and TAiBCs exhibited similar first oxidation potentials, those of TACs appeared at more positive potentials. These properties were reproduced and rationalized by molecular orbital and configuration interaction calculations within the framework of the ZINDO/S Hamiltonian. DFT-level frequency calculations have succeeded in reproducing the IR spectra for low-symmetry tetraazaporphyrin (TAP) derivatives for the first time. The relationship between structures and spectral features is discussed.