Heteroaromatic compounds having two-photon absorption activity

A compound of the formula (I)

• 10
• wherein het-1 and het-3 are identical or different, and are selected among the following heterocyclic groups:
• 11
• wherein X may be O, S or Se, and wherein R5 and R6 are the same or different, and are selected from the group consisting of H, alkyl groups having from 1 to 18 carbon atoms, alkoxy, aminoalkyl, alkylhalide, hydroxyalkyl, alkoalkyl, alkysulfide, alkylthiol, alkylazide, alkylcarboxyclic, alkylsulfonic, alkylisocyanate, alkylisothiocyanate, alkylalkene, alkylalkyne, aryl, and that can contain electronpoor ethenylic moieties such as maleimide, capable to react with nucleophilic groups such as —SH;
• and Het-2 is selected among the following heterocyclic-groups:
• 12
• wherein Y may be O, S, NZ, wherein Z=H, lower alkyl, aryl;
• and R7 and R8 may be the same or different, and are lower alkyl, lower alkoxy or hydroxyalkyl;
• wherein n=1, 2, and A is selected among the anions alkylsulfonate, arylsulfonate, triflate, halide, sulfate, phosphate;
• and wherein R1, R2, R3, R4, the same or different, are indipendenty selected from the group of H, lower alkyl, alkoxyalkyl, aryl, cyano, alkoxycarbonyl, —(CR9R10)m-Het, wherein 0<m<10, R9 and R10, the same or different, are selected from the group of H, lower alkyl, and Het may be Het-1 or Het-2 or Het-3.