Structure, Vibrations and Raman Modes in Electron Doped Metal Phthalocyanines

Dianionic Titanyl and Vanadyl (Cation+ )2 [MIV O(Pc4- )]2- Phthalocyanine Salts Containing Pc4- Macrocycles

In this study, the titanyl and vanadyl phthalocyanine (Pc) salts (Bu₄ N⁺ )₂ [M^IV O(Pc^4- )]^2- (M=Ti, V) and (Bu₃ MeP⁺ )₂ [M^IV O(Pc^4- )]^2- (M=Ti, V) with [M^IV O(Pc^4- )]^2- dianions were synthesized and characterized. Reduction of M^IV O(Pc^2- ) carried out with an excess of sodium fluorenone ketyl in the presence of Bu₄ N⁺ or Bu₃ MeP⁺ is exclusive to the phthalocyanine centers, forming Pc^4- species. During reduction, the metal +4 charge did not change, implying that Pc is an non-innocent ligand. The Pc negative charge increase caused the C-N(pyr) bonds to elongate and the C-N(imine) bonds to alternate, thus increasing the distortion of Pc. Jahn-Teller effects are significant in the [eg(π*)]² dianion ground state and can additionally distort the Pc macrocycles. Blueshifts of the Soret and Q-bands were observed in the UV/Vis/NIR when M^IV O(Pc^2- ) was reduced to [M^IV O(Pc^.3- )]^.- and [M^IV O(Pc^4- )]^2- . From magnetic measurements, [Ti^IV O(Pc^4- )]^2- was found to be diamagnetic and (Bu₄ N⁺ )₂ [V^IV O(Pc^4- )]^2- and (Bu₃ MeP⁺ )₂ [V^IV O(Pc^4- )]^2- were found to have magnetic moments of 1.72-1.78 μ_B corresponding to an S=1/2 spin state owing to V^IV electron spin. As a result, two latter salts show EPR signals with V^IV hyperfine coupling.

Salts with titanyl and vanadyl phthalocyanine radical anions. Molecular design and effect of cations on the structure and magnetic and optical properties

Our recent data on radical anion salts of titanyl (Ti^IVOPc) and vanadyl (V^IVOPc) phthalocyanines as well as additional new data are summarized.

Ultrafast charge transfer in nickel phthalocyanine probed by femtosecond Raman-induced Kerr effect spectroscopy

The recently developed technique of femtosecond stimulated Raman spectroscopy, and its variant, femtosecond Raman-induced Kerr effect spectroscopy (FRIKES), offer access to ultrafast excited-state dynamics via structurally specific vibrational spectra. We have used FRIKES to study the photoexcitation dynamics of nickel(II) phthalocyanine with eight butoxy substituents, NiPc(OBu)8. NiPc(OBu)8 is reported to have a relatively long-lived ligand-to-metal charge-transfer (LMCT) state, an essential characteristic for efficient electron transfer in photocatalysis. Following photoexcitation, vibrational transitions in the FRIKES spectra, assignable to phthalocyanine ring modes, evolve on the femtosecond to picosecond time scales. Correlation of ring core size with the frequency of the ν10 (asymmetric C-N stretching) mode confirms the identity of the LMCT state, which has a ∼500 ps lifetime, as well as that of a precursor d-d excited state. An even earlier (∼0.2 ps) transient is observed and tentatively assigned to a higher-lying Jahn-Teller-active LMCT state. This study illustrates the power of FRIKES spectroscopy in elucidating ultrafast molecular dynamics.