Raman Spectroscopy and Theoretical Characterization of Nanohybrids of Porphyrins with Carbon Nanotubes

Abstract

Single-walled carbon nanotube (SWCNT) hybrids with meso-5,10,15,20-tetrakis(N-methyl-4-pyridyl)porphyrin (TMPyP4) and meso-5,10,15,20-tetraphenylporphyrin (TPP) have been studied by the resonance Raman spectroscopy and by ab initio and molecular dynamic calculations. A comparison of the intensities of the bands assigned in the Raman spectrum to the radial breathing mode, as well as the relative band positions corresponding to the tangential modes of the hybrids with respect to the positions of these modes in the spectrum of the pristine SWCNT, indicates that the interaction of the nanotube with TMPyP4 is stronger than with TPP. A structure calculation (by the DFT/M05-2X method) of the TMPyP4 molecule adsorbed to a fragment of the zigzag (10,0) SWCNT surface shows that porphyrin adapts a saddled structure with the binding energy to the nanotube of −72.0 kcal/mol. The interaction energy in the complex of a TPP molecule with SWCNT, whose molecular structure is similar to TMPyP4, is only −19.3 kcal/mol and TP...