rising a linked compound formed by linking two compounds having the structure B wherein, RB is a hydrogen atom, or an alkyl secondary or tertiary amino substituent selected from the group consisting of 4-[4-aryl-N,N-dialkyl butylamine], 4-[4-heteroaromatic-N,N-dialkyl butylamine], 4-[4-aryl-N-alkyl butylamine] and 4-[4-heteroaromatic-N-alkyl butylamine]; R2 is a lower alkyl group; and R3 is a hydr