Patent ID: 8309728

Claim:
A compound of the general formula I where at least one of the R 1 , R 2 , R 3 and R 4 radicals is a substituent which is selected from Br, F and CN, and the remaining radicals are each hydrogen, Y 1 is O or NR a , where R a is hydrogen or an organyl radical, Y 2 is O or NR b , where R b is hydrogen or an organyl radical, Z 1 and Z 2 are each independently O or NR c , where R c is an organyl radical, Z 3 and Z 4 are each independently O or NR d , where R d is an organyl radical, where, in the case that Y 1 is NR a and at least one of the Z 1 and Z 2 radicals is NR c , R a with one R c radical may also together be a bridging group having 2 to 5 atoms between the flanking bonds, and where, in the case that Y 2 is NR b and at least one of the Z 3 and Z 4 radicals is NR d , R b with one R d radical may also together be a bridging group having 2 to 5 atoms between the flanking bonds, and provided that one of the following conditions apply: a) three of the R 1 , R 2 , R 3 and R 4 radicals are each bromine or are each fluorine or are each cyano, and the remaining radical is hydrogen; b) R 1 and R 2 are each independently selected from fluorine and cyano, and R 3 and R 4 are each hydrogen; c) R 1 and R 3 are each independently selected from fluorine and cyano, and R 2 and R 4 are each hydrogen; or d) R 1 and R 2 are each bromine, and R 3 and R 4 are each hydrogen.