Substituted Position Effect on Twisted intramolecular Charge Transfer of 1- and 2-anthracene aromatic Carboxamides as Chemosensors Based on Linear Polyether

Abstract

Bi-chromophoric compounds linked to linear polyether N,N'-[oxybis(3-oxapentamethyleneoxy-2-phenyl)]-bis(1-anthracenecarboxamide) (1(4)) and its analogues (1(5), 2(4) and 2(5)) were synthesized. Their photochemical properties and complexation actions were investigated in acetonitrile. These fluoroionophores have shown weak emissions in the absence of guest ions, resulting in a twisted intramolecular charge transfer (TICT) quenching process (off state) of an anthracene aromatic amide moiety. After the formation of a complex with alkaline earth metal ions, a large enhancement of fluorescent intensities was obtained (on state). The efficiencies of controlling an off-on fluorescent signal using 1(4) and its analogues (1(5), 2(4) and 2(5)) were larger than that of the 9-positioned analogue. These results suggested that the TICT relaxation process was effectively able to control using 1(4) and its analogues (1(5), 2(4) and 2(5)) by complex formations.