two or more R7 groups, if present, being either the same or different, p is an integer of 0-3, R8 individually represents a linear or branched alkyl group having 1-10 carbon atoms or a phenyl group or naphtyl group which may have a substituent, or two R11 groups bond, together with the sulfur atom to which the two R8 groups bond, to form a substituted or unsubstituted 3-11 member cyclic structure