Synthesis, fabrication of self-assembled film and ambipolar chemical sensing properties of triple-decker (phthalocyaninato) (porphyrinato) europium complex

Abstract

A mixed (phthalocyaninato) (porphyrinato) europium triple-decker complex, named (TPyP)Eu[Formula: see text][Pc(OC[Formula: see text]H[Formula: see text]][Formula: see text][TPyP [Formula: see text] dianion of 5,10,15,20-tetra(4-tert-pyridyl) porphyrin, Pc(OC[Formula: see text]H[Formula: see text] 2,3,9,10,16,17,23,24-octabutoxyphthalocyaninate] is synthesized and characterized by MALDI-TOF, 1HNMR, UV-visible spectra and differential pulse voltammetry techniques. Introduction of electron-donating butoxy groups at the periphery of the phthalocyanine ligands and electron-withdrawing pyridyl substituents onto the meso-positions of the porphyrin ring not only increases the solubility of the triple decker but successfully tunes the HOMO and LUMO energy levels into a soluble ambipolar organic semiconductor. A simple quasi-Langmuir–Shäfer (QLS) method is used to fabricate self-assembled film of (TPyP)Eu[Formula: see text][Pc(OC[Formula: see text]H[Formula: see text]][Formula: see text]. Excellent sensitivity, reproducible [Formula: see text]-type and [Formula: see text]-type responses to electron-accepting gas NO[Formula: see text] and electron-donating gas NH[Formula: see text] are found for the films of (TPyP)Eu[Formula: see text][Pc(OC[Formula: see text]H[Formula: see text]][Formula: see text]complex at room temperature. The detection limit towards NO[Formula: see text] and NH[Formula: see text] is as low as 0.4 ppm and 1 ppm, respectively, with percentage current change of 4.2% and 1.6%, depending on the uniform molecular packing and intermolecular interactions among the triple decker molecules. The present results represent not only the excellent example of ambipolar triple-decker phthalocyanine-based sensors obtained by a solution-based method, but more importantly provide a new strategy for the molecular design to obtain soluble ambipolar organic semiconductors in sensing device fabrication.