Tuning the optical properties of ZnTPP using carbonyl ring fusion.
Zinc meso-tetraphenylporphyrin (ZnTPP) was modified in such a way to allow the effect of an asymmetric structural distortion on its optical properties to be investigated. This involved the fusion of a phenyl group to an adjacent pyrrole ring via a carbonyl bridge. With the aid of Density Functional Theory (DFT) and time-dependent DFT (TD-DFT) calculations it was found that the asymmetric distortion away from planarity induced by the carbonyl fusion resulted in a loss of degeneracy in the two lowest unoccupied molecular orbitals (LUMOs). The effect was a red shift of the electronic absorbance bands, an increased Q:B ratio from 0.046 in ZnTPP to 0.096 in the fused derivative, and the appearance of additional UV-vis peaks. This study therefore suggests that structural distortions, as well as electronic substituents may be used to alter absorbance spectra, a technique which is of interest in the design of light-harvesting dyes.
Cleland
Deidre M
DM
Department of Chemistry and MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Otago, PO Box 56, Dunedin, New Zealand.
Gordon
Keith C
KC
Officer
David L
DL
Wagner
Pawel
P
Walsh
Penny J
PJ
D008665:Metalloporphyrins / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D011789:Quantum Theory; D013056:Spectrophotometry, Ultraviolet
D008665:Metalloporphyrins; C048955:zinc tetraphenylporphyrin