Photophysics of Octabutoxy Phthalocyaninato-Ni(II) in Toluene:  Ultrafast Experiments and DFT/TDDFT Studies

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Vol. 109; no. 10; pp. 2078 - 2089
• Main Authors: Gunaratne, Tissa C, Gusev, Alexey V, Peng, Xinzhan, Rosa, Angela, Ricciardi, Giampaolo, Baerends, Evert Jan, Rizzoli, Corrado, Kenney, Malcolm E, Rodgers, Michael A. J
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 17.03.2005
• Subjects: Computer Simulation; Crystallography, X-Ray; Light; Metalloporphyrins - chemistry; Models, Molecular; Molecular Structure; Organometallic Compounds - chemistry; Photochemistry; Quantum Theory; Solvents - chemistry; Time Factors; Toluene - chemistry
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp0457444

Reported herein is a combination of experimental and DFT/TDDFT theoretical investigations of the ground and excited states of 1,4,8,11,15,18,22,25-Octabutoxyphthalocyaninato-nickel(II), NiPc(BuO)8, and the dynamics of its deactivation after excitation into the S1(π,π*) state in toluene solution. According to X-ray crystallographic analysis NiPc(BuO)8 has a highly saddled structure in the solid state. However, DFT studies suggest that in solution the complex is likely to flap from one D 2 d -saddled conformation to the opposite one through a D 4 h -planar structure. The spectral and kinetic changes for the complex in toluene are understood in terms of the 730 nm excitation light generating a primarily excited S1 (π,π*) state that transforms initially into a vibrationally hot 3(d z 2 ,d x 2 - y 2 ) state. Cooling to the zeroth state is complete after ca. 8 ps. The cold (d,d) state converted to its daughter state, the 3LMCT (π,d x 2 - y 2 ), which itself decays to the ground state with a lifetime of 640 ps. The proposed deactivation mechanism applies to the D 2 d -saddled and the D 4 h -planar structure as well. The results presented here for NiPc(BuO)8 suggest that in nickel phthalocyanines the 1,3LMCT (π,d x 2 - y 2 ) states may provide effective routes for radiationless deactivation of the 1,3(π,π*) states.