A compound represented by formula (I). In the formula, R1 represents a hydrocarbon group of 1 to 10 carbon atoms; Z represents a hydrocarbon group of 1 to 10 carbon atoms or a cyano group; provided that R1 and Z may be mutually bonded to form a ring; X represents a divalent linking group having any one selected from —O—C(═O)—, —NH—C(═O)— and —NH—C(═NH)— on a terminal that comes into contact with Q; p represents an integer of 1 to 3; Q represents a hydrocarbon group having a valency of (p+1), provided that, when p is 1, Q may be a single bond; R2 represents a single bond, an alkylene group which may have a substituent or an arylene group which may have a substituent; q represents 0 or 1; r represents an integer of 0 to 8; and A+ represents a metal cation or an organic cation.