The charge-transfer constant. A new substituent constant for structure-activity relationships.

A new, versatile constant accounting for the pi-complex formation ability of aromatic systems is proposed. The constant is derived from charge-transfer complex data of aromatic species (charge-transfer constant, CT). The applicability of CT in structure-reactivity relations is demonstrated. It is shown that the affinity of various inhibitors (32) and acetylcholinesterase is a function of CT and pi (Hansch hydrophobicity constant).