“…Whereas efforts to improve its selectivity by introducing substituents to the central aromatic ring were not successful, 196 the use of a 1,8-naphthalenediol (Na + -3) instead of the catechol unit improved log K Na,K pot (SSM) to -0.7 and, upon further replacing the substituents on the nitrogens by cyclohexyl groups, to -1.3 (Na + -4, bis(1-butylpentyl)adipate). 197 A similar improvement in the discrimination of K + , accompanied by a smaller loss in that of Ca 2+ , was obtained by replacing the phenyl and benzyl groups of Na + -2 with cyclohexyl groups (Na + -5 (ETH 2120): log K Na,J pot (SSM): K + , -1.5; H + , -0.6; Li + , -1.2; Ca 2+ , -2.9; BBPA; log P TLC 8.3). 195,198 A recent report described the use of Na + -5 for ISFETs with fluorosilicone membranes (log K Na,J pot (FIM): K + , -1.8; Li + , -1.3; Ca 2+ , -3.0; NaTPB).…”