Langmuir–Blodgett films of substituted bis(naphthalocyaninato) rare earth complexes: structure and interaction with nitrogen dioxide

Abstract

Ordered molecular assemblies of novel alkylthio-substituted bis(naphthalocyaninato) rare earth complexes M[2,3-Nc(SC 12H 25) 8] 2 (M=Gd, Er) have been fabricated by Langmuir–Blodgett (LB) technique and characterized by surface pressure-area isotherm measurements, electronic absorption and polarized electronic absorption spectroscopy and low-angle X-ray diffractometry. The interaction between the thin films and NO 2 gas was investigated. The experimental results indicate that the bis(naphthalocyaninato) rare earth molecules form well-ordered stable monolayers with face-to-face orientation for the macrocycles and edge-on configuration for the molecules at the air–water interface and lamellar multilayers on solid substrates. The orientation angles of naphthalocyanine rings with respect to the quartz plate surface in the LB films for M[2,3-Nc(SC 12H 25) 8] 2 with M of Gd and Er have been determined based on the polarized absorbance and found to be 50° and 54°, respectively. The adsorption–desorption process of NO 2 on LB films of M[2,3-Nc(SC 12H 25) 8] 2 has been monitored by electronic absorption spectroscopy. A process of gas desorption was found to obey the Elovich equation.