Raman and UV-visible absorption spectra of ion-paired aggregates of copper porphyrins.
Raman and UV-visible absorption spectra of ion-paired aggregate constructed from two copper porphyrins, copper tetrakis(4-N-methylpyridyl)porphyrin (CuTMPyP) and copper tetrakis(4-sulfonatophenyl)pophyrin (CuTSPP), are reported in this paper. The absorption bands of the aggregate was found exhibiting obvious shift and broadening, which are attributed to the excitonic coupling between the two paired porphyrin rings. The excitonic coupling in the aggregates also induces evident alteration for Raman intensities compared with monomer spectrum. Aggregation results in only small shifts (2-3 cm(-1)) for Raman lines connecting with the vibrations of porphyrin rings, manifesting only slight structural change of porphyrin skeletons. On the other hand, evident downshift (5 cm(-1)) was observed for the Cm-pyridyl stretch mode (1254 cm(-1)) of CuTMPyP, suggesting weakening of the Cm-pyridyl bonds by aggregation. Raman depolarization ratios of the aggregates are different from those of the monomers, implying a lowering of effective symmetry due to the molecular packing in the aggregates.
Chen
Dong-Ming
DM
Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui, People's Republic of China. dmchen@ustc.edu.cn
Zhang
Ying-Hui
YH
He
Tian-Jing
TJ
Liu
Fan-Chen
FC
D003300:Copper; D008665:Metalloporphyrins / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D013053:Spectrophotometry / Q000379:methods; D013056:Spectrophotometry, Ultraviolet; D013059:Spectrum Analysis, Raman / Q000379:methods
D008665:Metalloporphyrins; C441603:meso-tetra(4-methylpyridinium)porphyrinato copper(II); D003300:Copper