Preliminary communication 13C CPMAS NMR of 5,10,15,20-tetrakis(4-n-dodecylphenyl)-porphyrin: dynamics of aliphatic chains in discotic lamellar mesophases

Abstract

Solid state 13C CPMAS NMR spectra of 5,10,15,20-tetrakis(4-n-dodecylphenyl)porphyrin (C12 TPP) have been studied to elucidate the microscopic structures and dynamics in the mesophases. The temperature dependence of 13C CPMAS NMR in the aliphatic regions is discussed mainly in relation to the phase transitions. The spectra for the aliphatic chains showed remarkable changes with the phase transition from crystal to lower mesophase (ML) and from lower to higher mesophase (ML). It was found that the aliphatic chains partially melt in the ML phase, while they melt totally in the ML phase. The spectra in the aromatic region did not vary greatly with the transitions from crystal to ML and from ML to ML, which probably means that the molecular D4h symmetries are distorted in these mesophases, as in the crystal, on the time scale observed by NMR (~kHz).