| abstract |
Described herein are compounds having the general formula: wherein: Ar1 and Ar2 are independently selected aryl groups, optionally substituted with substituents selected from the group consisting of alkyl, cycloalkyl, alkoxy, alkanoyl, aralkyl, aralkyloxy, halo, NO2, Ph, CF3, CN, OH, methylenedioxy, ethylenedioxy, SO2NRR', NRR', CO2R (where R and R' are independently selected from the group consisting of H and alkyl) and a second aryl group, which may be substituted as above; wherein any cycloalkyl or aryl substituent is linked to Ar1 or Ar2 by a bridging element which may be a single bond, a vinylene group, an ethynylene group, a Z group, a -Z-(CH2)n- group, a -(CH2)n-Z- group, or a -Z-(CH2)n-Z- group, where Z represents an O atom, a S atom, an NH group or an N-alkyl group, and n is an integer from 1 to 4; wherein Ar1 and Ar2 may be attached to the central atom to which they are connected by a single bond, an alkylene, alkenylene or alkynylene group; wherein Ar1 and Ar2 may be attached to the central atom to which they are connected by a single bond, an alkylene, alkenylene or alkynylene group; R3 is selected from the group consisting of H and aryl, which may be substituted as for Ar1; R4 and R5 are independently selected from the group consisting of H, alkyl, alkanoyl, benzoyl and benzyl. |