Synthesis and spectroscopic and electrochemical studies of novel benzo- or 2,3-naphtho-fused tetraazachlorins, bacteriochlorins, and isobacteriochlorins

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.     

Theoretical prediction of electronic structures of fully pi-conjugated zinc oligoporphyrins with curved surface structures

A theoretical prediction of the electronic structures of fully pi-conjugated zinc oligoporphyrins with curved surface, ring, tube, and ball-shaped structures was conducted as the objective for the future development of triply meso-meso-, beta-beta-, and beta-beta-linked planar zinc oligoporphyrins. The excitation energies and oscillator strengths for the optimal ring and ball structures were calculated using the time-dependent density functional theory (DFT). Although there is an extremely small energy difference of < 0.1 eV between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the ring structure relative to the same-sized triply linked planar one, the Q and B bands of the former are smaller redshifted excitation energies and intensified oscillator strengths than those of the latter due to the structurally shortened effective pi-conjugated lengths for the electron transition. It is expected that the ball structure becomes an excellent electron acceptor and shows the highly redshifted Q' band in the near-IR region relative to the monomer. The minimum value of the HOMO-LUMO energy gaps of the infinite-length ring structures was estimated using periodic boundary conditions within the DFT, resulting in the metallic characters of both the tube structures with and without the spiral triply linked porphyrin array. The relation between the diameters and strain energies of the tube and ball structures was also examined. The present fused zinc porphyrins may become more colorful materials with new optelectronic properties including artificial photosynthesis than the carbon nanotubes and fullerenes when the axial coordinations of the central metal of porphyrins are functionally used.     

Spectroscopic and theoretical studies of Ga(III)protoporphyrin-IX and its reactions with myoglobin

Ga(III)protoporphyrin-IX (Ga-PP) has been proposed as a model for the key interporphyrin interactions in malaria pigment. Unlike the paramagnetic parent iron heme derivatives, Ga-PP is readily soluble in methanol (MeOH). We report optical, mass spectroscopic, and theoretical results for Ga-PP as well as its reactions with myoglobin. UV-visible absorption and MCD spectroscopy show that Ga-PP exhibits a typical spectrum for a main group metal: a Q-band at 539 nm and a B band at 406 nm when dissolved in MeOH. We also report optical data for Zn(II)protoporphyrin IX (Zn-PP) dissolved in MeOH, which exhibits a Q-band at 545 nm and a B band at 415 nm. ESI mass spectral data for Ga-PP dissolved in MeOH show the presence of predominantly monomers, with smaller fractions of dimers [(Ga-PP)(2)] and trimers. UV-visible and MCD absorption spectroscopy and ESI mass spectral data demonstrate the successful insertion of monomeric Ga-PP into apo-Mb. Ga-PP-Mb exhibits a B band at 417 nm and Q bands at 545 and 584 nm, which are all red-shifted from the free Ga-PP values. The calculated electronic structures and frontier molecular orbitals of Ga-PP, (Ga-PP)(2) and Zn-PP fit the previously reported trends in band energies and oscillator strengths as a function of molecular orbital energies. These new data can be applied to explain the experimentally observed optical spectroscopy. The observed Q-band energies are accounted for by calculated (HOMO-LUMO) gap of the frontier MOs, while the split in the two top occupied MOs accounts for the magnitude of the Q-band oscillator strength as well as the experimentally observed Q to B band energy separation. Although Ga-PP shares more spectroscopic properties with Zn-PP than it does with Fe(III)PPIX, the trivalent oxidation state allows this molecule to be used as a model for ferric hemes in heme proteins.     

Spectroscopic and theoretical studies of optically active porphyrin dimers: a system uninterpretable by exciton coupling theory.

The electronic excited states of a meso-meso beta-beta doubly linked bis-porphyrin are comprehensively investigated by measuring its circular dichroism (CD) and magnetic circular dichroism (MCD) spectra. The observed spectroscopic properties are rationalized by DFT calculations. The frontier molecular orbitals (MOs) are constructed by the linear combinations of the constituent monomers' four MOs. Comparison of a theoretical CD spectrum based on time-dependent DFT (TDDFT) with the experimental spectra resulted in the assignment of the helical conformation of the dimer. This assignment is contrary to the previous assignment based on the point-dipole approximation (exciton coupling theory).     

ZINDO calculations of the ground state and electronic transitions in the tetracyanonickelate Ion,Ni(CN)(4)(2-)

ZINDO semiempirical calculations on the Ni(CN)(4)(2-) ion were performed, and ground-state energies for all 41 valence-orbital-based MOs and orbital transition components of the two lowest energy fully allowed electronic transitions are reported. Gaussian 94 was used to calculate ground-state energies as a comparison. The ground-state energies using ZINDO compare much more favorably with those found through ab initio techniques than with those from a reported INDO calculation. The found electronic transitions agree substantially with earlier assignments with the exception that several orbital transitions are required to adequately model the lowest energy allowed x,y-polarized experimental transition. Calculation parameters were optimized to give excellent agreement with experiment and may serve well for more complex arrangements of this ion.     

Low‐Symmetry Ω‐Shaped Zinc Phthalocyanine Sensitizers with Panchromatic Light‐Harvesting Properties for Dye‐Sensitized Solar Cells

Two low‐symmetry phthalocyanines (Pcs) substituted with thiophene units at the non‐peripheral (α) and peripheral (β) positions were synthesized and their optical, electronic‐structure, and electrochemical properties were investigated. The substitution of thiophene units at the α positions of the phthalocyanine skeleton resulted in a red shift of the Q band and significantly modified the molecular‐orbital electronic distributions just below the HOMO and just above the LUMO, with distortion of the typical Gouterman four‐orbital arrangement of MOs. Two amphiphilic Ω‐shaped ZnPcs ( αPcS1 and αPcS2 ) bearing a π‐conjugated side chain with an adsorption site at an α position of the Pc macrocycle were synthesized as sensitizers for dye‐sensitized solar cells (DSSCs). The absorption spectra of αPcS1 and αPcS2 showed red shifted Q bands and a broad band from 350 to 550 nm assignable to the intramolecular charge‐transfer transition from the ZnPc core to the side chains. Time‐dependent DFT calculations provided a clear interpretation of the effect of the thiophene conjugation on the typical phthalocyanine core π MOs. Compound αPcS1 was used as a light‐harvesting dye on a TiO₂ electrode for a DSSC, which showed a panchromatic response in the range 400–800 nm with a power conversion efficiency of 5.5 % under one‐sun conditions.     

Magnetic circular dichroism of porphyrins containing M = Ca, Ni, and Zn. A computational study based on time-dependent density functional theory

A theoretical study is presented on the magnetic circular dichroism (MCD) exhibited by the porphyrin complexes MP (M = Mg,Ni,Zn), MTPP (M = Mg,Ni,Zn), and NiOEP, where P = porphyrin, TPP = tetraphenylporphyrin, and OEP = octaethylporphyrin. The study makes use of a newly implemented method for the calculation of A and B terms from the theory of MCD and is based on time-dependent density functional theory (TD-DFT). It is shown that the MCD spectrum is dominated by a single positive A term in the Q-band region in agreement with experiment where available. The band can be fully explained as the first transition in Gouterman's four-orbital model for the type of porphyrins studied here. For the Soret band, the experimental MCD spectrum appears as a single positive A term. This is also what is found computationally for NiP and NiTPP, where the second transition in Gouterman's four-orbital model give rise to a positive A term. However, for the remaining systems, the simulated MCD spectrum is actually due to two B terms that have the appearance of one positive pseudo A term. The two B terms appear because the second Gouterman state is coupled strongly to a second excited state (b(2u) --> 2e(g)) of nearly the same energy by the external magnetic field.     

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

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.     

Detailed assignment of the magnetic circular dichroism and UV-vis spectra of five-coordinate high-spin ferric [Fe(TPP)(Cl)

High-spin (hs) ferric heme centers occur in the catalytic or redox cycles of many metalloproteins and exhibit very complicated magnetic circular dichroism (MCD) and UV-vis absorption spectra. Therefore, detailed assignments of the MCD spectra of these species are missing. In this study, the electronic spectra (MCD and UV-vis) of the five-coordinate hs ferric model complex [Fe(TPP)(Cl)] are analyzed and assigned for the first time. A correlated fit of the absorption and low-temperature MCD spectra of [Fe(TPP)(Cl)] lead to the identification of at least 20 different electronic transitions. The assignments of these spectra are based on the following: (a) variable temperature and variable field saturation data, (b) time-dependent density functional theory calculations, (c) MCD pseudo A-terms, and (d) correlation to resonance Raman (rRaman) data to validate the assignments. From these results, a number of puzzling questions about the electronic spectra of [Fe(TPP)(Cl)] are answered. The Soret band in [Fe(TPP)(Cl)] is split into three components because one of its components is mixed with the porphyrin A2u72-->Eg82/83 (pi-->pi*) transition. The broad, intense absorption feature at higher energy from the Soret band is due to one of the Soret components and a mixed sigma and pi chloro to iron CT transition. The high-temperature MCD data allow for the identification of the Q v band at 20 202 cm(-1), which corresponds to the C-term feature at 20 150 cm(-1). Q is not observed but can be localized by correlation to rRaman data published before. Finally, the low energy absorption band around 650 nm is assigned to two P-->Fe charge transfer transitions, one being the long sought after A1u(HOMO)-->d pi transition.     

Theoretical Study of Electronic Structures and Spectra of Chalcogenido Complexes of Molybdenum, trans-Mo(Q)(2)(PH(3))(4) (Q = O, S, Se, Te)

Electronic structures of the title complexes have been studied using quantum chemical computations by different methods. It is shown that the results of Xalpha calculations agree well with expectations from classical ligand-field theory, but both are far from being in agreement with the results given by ab initio calculations. The HOMO in the ab initio Hartree-Fock molecular orbital diagrams of all these complexes is a chalcogen p(pi) lone pair orbital rather than the metal nonbonding d(xy)() orbital previously proposed. Electronic transition energies were calculated by CASSCF and CI methods. The results suggest that in the cases when Q = S, Se, and Te the lowest energy transitions should be those from the p(pi) lone pair orbitals to the metal-chalcogen pi orbitals. The calculated and observed electronic spectra of the oxo complex are in good agreement and very different from the spectra of the other complexes, and the lowest absorptions were accordingly assigned to transitions of different origins.     

Charge-transfer interaction of aromatic thiols with 2,3-dichloro-5,6-dicyano-p-benzoquinone: spectral and quantum mechanical studies

Charge-transfer (CT) complexes formed between aromatic thiol donors (thiophenol (TP), benzene-1,4-dithiol (BDT), p-aminothiophenol (ATP), p-hydroxythiophenol (HTP), and p-toluenethiol (TTP)) and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) as an acceptor were studied spectrophotometrically in dichloromethane. Addition of aromatic thiols in dichloromethane to DDQ leads to the formation of colored solutions that exhibit a very broad absorption band in the range 440-800 nm and a band in the region 300-400 nm. On the basis of the energies of LUMO and HOMO from quantum mechanical calculations, the broad band observed in the visible region was assigned to the pi*(a2) <-- pi(b1) transition and a band observed between 300 and 400 nm was assigned to the pi*(a2) <-- pi(a2) transition. The solid CT complexes of aromatic thiols and DDQ were prepared and characterized by FT-IR spectroscopy. The stoichiometry of the CT complexes was determined by Job's continuous variation method. The association constant (KCT), molar extinction coefficient (epsilon), oscillator strength (f), and transition dipole moment (micro) values were calculated from the electronic spectra. The vertical ionization potentials (ID) of the donors were calculated from their corresponding lambdaCT. Quantum mechanical (QM) calculations were performed to determine the ionization potential and the energies of the highest occupied molecular orbital (HOMO) of donors and lowest unoccupied molecular orbital (LUMO) of an acceptor.     

Calculation of the magnetic circular dichroism B term from the imaginary part of the Verdet constant using damped time-dependent density functional theory

A time-dependent density functional theory (TDDFT) formalism with damping for the calculation of the magnetic optical rotatory dispersion and magnetic circular dichroism (MCD) from the complex Verdet constant is presented. For a justification of such an approach, we have derived the TDDFT analog of the sum-over-states formula for the Verdet constant. The results of the MCD calculations by this method for ethylene, furan, thiophene, selenophene, tellurophene, and pyrrole are in good agreement with our previous theoretical sum-over-states MCD spectra. For the pi-->pi(*) transition of propene, we have obtained a positive Faraday B term. It is located between the two negative B terms. This finding is in agreement with experiment in the range of 6-8 eV.     

Calculations of the optical spectra of hydrocarbon radical cations based on Koopmans' theorem

The first few bands in the optical spectra of radical cations can often be interpreted in terms of A-type transitions that involve electron promotions from doubly occupied to the singly occupied molecular orbital (SOMO) and/or B-type transition which involve electron promotion from the SOMO to virtual molecular orbitals. We had previously demonstrated that, by making use of Koopmans' theorem, the energies of A-type transitions can be related to orbital energy differences between lower occupied MOs and the highest occupied MO (HOMO) in the neutral molecule, calculated at the geometry of the radical cation. We now propose that the energies of B-type transitions can be related similarly to energy differences between the lowest unoccupied MO (LUMO) and higher virtual MOs in the dication, also calculated at the geometry of the radical cation, by way of an extension of Koopmans' theorem to virtual MOs similar to that used sometimes to model resonances in electron scattering experiments. The optical spectra of the radical cations of several polyenes and aromatic compounds, the matrix spectra of which are known (or presented here for the first time), and for which CASSCF/CASPT2 calculations are available, are discussed in terms of these Koopmans-based models. Then the spectra of five poly(bicycloalkyl)-protected systems and that of hexabenzocoronene, compounds not amenable to higher level calculations, are examined and it is found that the Koopmans-type calculations allow a satisfactory interpretation of most of the features in these spectra. These simple calculations therefore provide a computationally inexpensive yet effective way to assign optical transitions in radical ions. Limitations of the model are discussed.     

Identification of the alkalide,Na−, in Na/NH3 matrices using MCD

Codeposition of Na and NH₃ at ≈ 35 K gives rise to an absorption band at ≈ 16950 cm⁻¹ with a positive MCD å term. This band is assigned to the ¹S → ¹P transition of Na⁻ marking the first direct evidence for the existence of an alkalide in NH₃. The absorption and MCD of the solvated electron band are also observed in the near infrared at ≈ 8000 cm⁻¹.     

Piezochromism in nickel salicylaldoximato complexes: tuning crystal-field splitting with high pressure

The crystal structures of bis(3-fluoro-salicylaldoximato)nickel(II) and bis(3-methoxy-salicylaldoximato)nickel(II) have been determined at room temperature between ambient pressure and approximately 6?GPa. The principal effect of pressure is to reduce intermolecular contact distances. In the fluoro system molecules are stacked, and the Ni???Ni distance decreases from 3.19?? at ambient pressure to 2.82?? at 5.4?GPa. These data are similar to those observed in bis(dimethylglyoximato)nickel(II) over a similar pressure range, though contrary to that system, and in spite of their structural similarity, the salicyloximato does not become conducting at high pressure. Ni-ligand distances also shorten, on average by 0.017 and 0.011?? for the fluoro and methoxy complexes, respectively. Bond compression is small if the bond in question is directed towards an interstitial void. A band at 620?nm, which occurs in the visible spectrum of each derivative, can be assigned to a transition to an antibonding molecular orbital based on the metal 3d(x(2)-y(2)) orbital. Time-dependent density functional theory calculations show that the energy of this orbital is sensitive to pressure, increasing in energy as the Ni-ligand distances are compressed, and consequently increasing the energy of the transition. The resulting blueshift of the UV-visible band leads to piezochromism, and crystals of both complexes, which are green at ambient pressure, become red at 5?GPa.     

Magnetic circular dichroism of phthalocyanine (m=mg, zn) and tetraazaporphyrin (m=mg, zn, ni) metal complexes. A computational study based on time-dependent density functional theory

We present here simulated magnetic circular dichroism (MCD) spectra of MTAP (M=Mg, Ni, Zn) and MPc (M=Mg, Zn) where TAP=tetraazaporphyrin and Pc=phthalocyanine. The study is based on magnetically perturbed time-dependent density functional theory (MP-TDDFT) and a newly implemented method for the calculation of A and B terms from the theory of MCD. It follows from our investigation that the MCD spectrum for the MTAP and MPc systems in the Q-band region consists of a single positive A term augmented by a positive B term, in agreement with experiment where available. The Q band can be fully characterized in terms of the 2a1u-->2eg one-electron excitation. For the aza systems MgTAP and ZnTAP, the simulated MCD spectra in the Soret region are dominated by the two one-electron excitations 2a2u-->2eg and 1a2u-->2eg and has the appearance of a positive A term (with values between 1.33-1.55, depending on the MTAP system) made asymmetric by a negative B term, in good agreement with experiment. We find, in agreement with all available experimental findings on MPc (M=Mg, Zn) type systems, that the MCD spectra in the Soret region are dominated by two transitions with positive A/ D-term values and two negative B/ D-term values. The major contribution to the two transitions comes from the 2a2u-->2eg and 1a2u-->2eg one-electron excitations. It appears that the ratio of A/ B for the term parameters is underestimated by theory.     

Piezochromism in Nickel Salicylaldoximato Complexes: Tuning Crystal‐Field Splitting with High Pressure

The crystal structures of bis(3‐fluoro‐salicylaldoximato)nickel(II) and bis(3‐methoxy‐salicylaldoximato)nickel(II) have been determined at room temperature between ambient pressure and approximately 6 GPa. The principal effect of pressure is to reduce intermolecular contact distances. In the fluoro system molecules are stacked, and the Ni???Ni distance decreases from 3.19 Å at ambient pressure to 2.82 Å at 5.4 GPa. These data are similar to those observed in bis(dimethylglyoximato)nickel(II) over a similar pressure range, though contrary to that system, and in spite of their structural similarity, the salicyloximato does not become conducting at high pressure. Ni–ligand distances also shorten, on average by 0.017 and 0.011 Å for the fluoro and methoxy complexes, respectively. Bond compression is small if the bond in question is directed towards an interstitial void. A band at 620 nm, which occurs in the visible spectrum of each derivative, can be assigned to a transition to an antibonding molecular orbital based on the metal 3d(x²?y²) orbital. Time‐dependent density functional theory calculations show that the energy of this orbital is sensitive to pressure, increasing in energy as the Ni–ligand distances are compressed, and consequently increasing the energy of the transition. The resulting blueshift of the UV‐visible band leads to piezochromism, and crystals of both complexes, which are green at ambient pressure, become red at 5 GPa.     

Application of MCD spectroscopy and TD-DFT to a highly non-planar porphyrinoid ring system. New insights on red-shifted porphyrinoid spectral bands

The first magnetic circular dichroism (MCD) spectra are reported for tetraphenyltetraacenaphthoporphyrin (TPTANP). The impact on the electronic structure of steric interactions between the fused acenaphthalene rings and the meso-tetraphenyl substituents is explored based on an analysis of the optical spectra of the Zn(II) complex (ZnTPTANP) and the free base dication species ([H4TPTANP]2+). In the case of ZnTPTANP, significant folding of the porphyrinoid ligand induces a highly unusual MCD-sign reversal providing the first direct spectroscopic evidence of ligand nonplanarity. Density functional theory (DFT) geometry optimizations for a wide range of Zn(II) porphyrinoids based on the B3LYP functional and TD-DFT calculations of the associated UV-visible absorption spectra are reported, allowing a complete assessment of the MCD data. TPTANP complexes are found to fall into a class of cyclic polyenes, termed as soft MCD chromophores by Michl (J. Pure Appl. Chem. 1980, 52, 1549.), since the signs of the Faraday A1 terms observed in the MCD spectrum are highly sensitive to slight structural changes. The origin of an unusually large red shift of the main B (or Soret) band of MTPTANP (the most red shifted ever reported for fused-ring-expanded metal porphines) and of similar red shifts observed in the spectra of other peripherally crowded porphyrinoid complexes is also explored and explained on this basis.     

Electronic structure of reduced symmetry peripheral fused-ring-substituted phthalocyanines

Reduced symmetry phthalocyanines are finding use in an increasing number of industrial applications. A detailed understanding of the electronic structure of the pi-system will greatly facilitate the design of new complexes, which fit the specifications required in many of these emerging high technology fields. NMR, electronic absorption, magnetic circular dichroism (MCD), and fluorescence emission and excitation spectra have been recorded for five generic metal phthalocyanine (MPc) derivatives in which additional benzene rings are fused either radially or obliquely onto at least one of the four peripheral benzo groups. The spectroscopy of four radially substituted compounds, zinc mononaphthotribenzotetraazaporphyrine (Zn3B1N), zinc monobenzotrinaphthotetraazaporphyrine (Zn1B3N), and two cis and trans zinc dibenzodinaphthotetraazaporphyrine (Zn2B2N) isomers, is compared to that of the obliquely fused structural isomer of Zn3B1N (Zn3BoN) and the D(4)(h)() symmetry parent compounds, ZnPc and zinc naphthalocyanine (ZnNc). The selection of Zn(II) as the central metal eliminates the possibility of charge transfer between the metal and ring. None of the complexes studied contain any sigma-bonded peripheral substituents. (1)H NMR signals of the seven compounds are assigned on the basis of the coupling patterns, integrated proton numbers, and decoupling experiments. The SIMPFIT program was used to perform spectral band deconvolution analyses of absorption and MCD spectra. ZINDO molecular orbital calculations are described, and the optical spectra are assigned on the basis of the MO models that have been developed previously to account for the spectral properties of metal porphyrin (MP(-2)) and metal phthalocyanine (MPc(-2)) complexes.