Photophysics of octabutoxy phthalocyaninato-Ni(II) in toluene: ultrafast experiments and DFT/TDDFT studies.

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 S(1)(pi,pi) 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.

Excited state relaxation dynamics of the zinc(II) tetraphenylporphine cation radical.

A new technique employed to study the photophysical properties of the zinc(II) tetraphenylporphine cation radical is reported. It employs a combination of controlled potential coulometry and femtosecond absorption spectrometry. The fast transient lifetime of 17 ps of the pi-cation species originates in very efficient mixing of the a(2u) HOMO cation orbital that places electronic density mainly on pyrrolic nitrogens and metal d-orbitals.

Making a molecular wire: charge and spin transport through para-phenylene oligomers.

Functional molecular wires are essential for the development of molecular electronics. Charge transport through molecules occurs primarily by means of two mechanisms, coherent superexchange and incoherent charge hopping. Rates of charge transport through molecules in which superexchange dominates decrease approximately exponentially with distance, which precludes using these molecules as effective molecular wires.

Excited-state symmetry breaking in cofacial and linear dimers of a green perylenediimide chlorophyll analogue leading to ultrafast charge separation.

Photoexcitation of chromophoric dimers constrained to a symmetric pi-stacked geometry by their molecular structure usually produces excimers independent of solvent polarity, while dimers with edge-to-edge perpendicular pi systems undergo excited-state symmetry breaking in highly polar solvents leading to intradimer charge separation. We present direct evidence for symmetry breaking in the lowest excited singlet state of a symmetric cofacial dimer of 1,7-bis(pyrrolidin-1'-yl)-perylene-3,4:9,10-bis(dicarboximide) (5PDI) in the low polarity solvent toluene to produce a radical ion pair quantitatively. This dimer, cof-5PDI2, was synthesized by attaching two 5PDI chromophores via imide groups to a xanthene spacer.