Simulation And Approach Of S₀â†'S₁Fine Electronic Spectrum Of Several Porphyrins And Their Derivatives

This work focused on the structure, spectra and relationship of several porphyrins and their derivatives (Porphycene (Pc), Magnesium Porphyrin (MgP), Znic tetraazaporphyrin (ZnTAP), tetraazaporphyrin (H2TAP) and Phthalocyanine (H2PC) molecules) with three hybrid functionals (B3LYP, BhandHLYP and PBEO). Based on the accurate calculations of equilibrium geometries with B3LYP (Pc, H2TAP and H2Pc) and BHandHLYP (MgP and ZnTAP) functionals, the vibrationally resolved absorption spectra including Herzberg-Teller and Duschinsky contributions were simulated in the Franck-Condon approximation. Results indicated that most of vibrational transitions were reproduced correctly. Furthermore, considering Herzberg-Teller and Duschinsky effects were important and cannot be ingnored.1. The simulation of S0â†'S1absorptiona spectra for Porphycene (Pc), Magnesium Porphyrin (MgP) and Znic-tetraazaporphyrin (ZnTAP)Few theoretical investigations were performed to simulate the well resolved spectra and assign the vibronic bands of porphyrin and its derivatives due to the difficulties of optimization the excited states and analysis a large number of final vibrational-normal modes. The four isomers (two trans A and B, two cis C and D) were formed by hydrogen transfer of Pc molecule, a potential energy profile confirmed that the most stable isomer was trans A configuration. Geometry optimization on the trans A without no symmetric constraint estimated that trans A belonged to C2h point symmetry. The high-resolved S0â†'S1absorption spectra of Pc, MgP and ZnTAP were simulated including the Duschinsky and Herzberg-Teller effects in the Franck-Condon approximation. The theoretical results provid a good description for the optical spectra and revealed that HT induced mechanism play an important role in simulation spectra. Furthermore, we tentatively assigned several bands which appeared in experimental observations but the corresponding assignments were not given. Our simulated spectra were nicely agreement with the experimental spectra.2. The simulation of Qx band absorption for tetraazaporphyrin and PhthalocyanineAll key structural parameters, vertical excitation energies, oscillator strengths and frequencies of phthalocyanine (H2PC) and tetraazaporphyrin (H2TAP) with B3LYP functional agreed well with the experimental data. The calculated results indicated that the Q band shift to lower energy and split decreasing with the extension of the tetraazaporphyrin. The vibrationally resolved absorption spectra of Qx band of H2TAP and H2PC were simulated using Franck-Condon approximation. Especially, the noticeable Duschinsky and Herzberg-Teller contributions for the well-resolved absorption spectra were considered. Experiment and our calculation results revealed that S2state of H2PC, located around1000cm-1from v0-0of S1, could induce a coupling with excited vibrational levels of the Si state-the electronic analogue of Fermi resonance. The present calculation reproduced correctly most of vibrational transitions in the experimental observations. Moreover, we attempted to assign a few bands which were not unambiguously assiged in the experimental spectrum of H2TAP molecule.