Patent ID: 7268095

Claim:
A compound of the formula Ia or Ib where, in the formula Ia, E 1 is O, S, Se, Te, NR, CR 2 , or PR; E 2 , E 3 are each CR, N, P; E 4 is N, or P; E 5 is OH, SH, NHR, OR′, SR′, or NRR′; E 6 is NH, PH, NR′, or PR′; R 5 , R 6 are each hydrogen or a linear, branched or cyclic alkyl radical or an aryl radical; R 1 , R 2 , R 3 , R 4 are each hydrogen, a linear, branched or cyclic alkyl radical, an aryl radical, a halogen or a nitro group; R is hydrogen, a linear, branched or cyclic alkyl radical; R′ is a linear, branched or cyclic alkyl radical; where at least one of the groups E 5 and E 6 contains a hydrogen atom; and in the formula Ib, the symbols E 1 , E 4 , E 5 , E 6 , R 5 , R 6 , R 1 , R 2 , R 3 , R 4 , R and R′ are as defined in formula Ia; and E′ 2 and E′ 3 are each O, S, Se, Te, NR, CR 2 , or PR.