Synthesis, characterization and ethanol sensing properties of carboxylic acid-terminated naphthoxy substituted phthalocyanines

•Synthesis of carboxylic acid-terminated naphthoxy substituted free metal and metallophthalocyanines.•An ethanol sensor based on Pc compounds is proposed and investigated.•The influence of COOH group on the ethanol vapor sensing properties.•Highly sensitive detection of ethanol vapor by [2,9,16,23-tetra-(4-(6-carboxy-2-naphthoxy)-phthalocyaninato-nickel (II)].•Both surface ionization energy of central metal atom and oxygen-displacement play role in the ethanol adsorption.