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A time-dependent density functional theory (TDDFT) approach coupled with 14 different exchange-correlation functionals was used for the prediction of vertical excitation energies in zinc phthalocyanine (PcZn). In general, the TDDFT approach provides a more accurate description of both visible and ultraviolet regions of the UV−vis and magnetic circular dichroism (MCD) spectra of PcZn in comparison to the more popular semiempirical ZINDO/S and PM3 methods. It was found that the calculated vertical excitation energies of PcZn correlate with the amount of Hartree−Fock exchange involved in the exchange-correlation functional. The correlation was explained on the basis of the calculated difference in energy between occupied and unoccupied molecular orbitals. The influence of PcZn geometry, optimized using different exchange-correlation functionals, on the calculated vertical excitation energies in PcZn was found to be relatively small. The influence of solvents on the calculated vertical excitation energies in PcZn was considered for the first time using a polarized continuum model TDDFT (PCM-TDDFT) method and was found to be relatively small in excellent agreement with the experimental data. For all tested TDDFT and PCM-TDDFT cases, an assignment of the Q-band as an almost pure a1u(HOMO) → eg(LUMO) transition, initially suggested by Gouterman, was confirmed. Pure exchange-correlation functionals indicate the presence of six 1Eustates in the B-band region of the UV−vis spectrum of PcZn, while hybrid exchange-correlation functionals predict only five 1Eustates for the same energy envelope. The first two symmetry-forbidden n → transitions were predicted in the Q0-2region and in the low-energy tail of the B-band, while the first two symmetry-allowed n → transitions were found within the B-band energy envelope when pure exchange-correlation functionals were used for TDDFT calculations. The presence of a symmetry-forbidden but vibronically allowed n → transition in the Q0-2spectral envelope explains the long-time controversy between the experimentally observed low-intensity transition in the Q0-2region and previous semiempirical and TDDFT calculations, which were unable to predict any electronic transitions in this area. To prove the conceptual possibility of the presence of several degenerate 1Eustates in the B-band region of PcZn, room-temperature UV−vis and MCD spectra of zinc tetra-tert-butylphthalocyanine (PctZn) in non-coordinating solvents were recorded and analyzed using band deconvolution analysis. It was found that the B-band region of the UV−vis and MCD spectra of PctZn can be easily deconvoluted using six MCD Faraday A-terms and two MCD Faraday B-terms with energies close to those predicted by TDDFT calculations for 1Euand 1A2uexcited states, respectively. Such a good agreement between theory and experiment clearly indicates the possibility of employing a TDDFT approach for the accurate prediction of vertical excitation energies in phthalocyanines within a large energy range. [ABSTRACT FROM AUTHOR]

A direct reaction between ferrocene (FcH) and tetracyanoethylene (TCNE) in various solvents and within a wide range of temperatures has been investigated in order to optimize the preparation of tricyanovinylferrocene. Under optimized reaction conditions, tricyanovinylferrocene was prepared in ∼26% yield along with cyanoferrocene as a major reaction product in the reaction between 1 equiv of FcH and 2 equiv of TCNE for 10 min in sulfolane at 110 °C. It was proposed that the reaction proceeds via a single-electron-transfer step, which results in the formation of a spectroscopically detected FcH•TCNE•-intermediate followed by homolytic cleavage of the C−CN bond. The possible phase transition in tricyanovinylferrocene has been tested by X-ray crystallography at 173 and 293 K. The prominent visible band observed in the UV−vis spectrum of tricyanovinylferrocene has been unambiguously assigned to a metal-to-ligand charge-transfer transition on the basis of experimental and theoretical (TDDFT) data, while its solvatochromic behavior was tested using the Kamlet−Taft model. It has been found that the solvatochromism observed in tricyanovinylferrocene predominantly depends on the value of dipolarity/polarizability parameter in the Kamlet−Taft equation. The significant anisotropy of the quadrupole doublet in the Mössbauer spectra of tricyanovinylferrocene and cyanoferrocene was explained on the basis of DFT calculations. [ABSTRACT FROM AUTHOR]