Patent ID: 6979681

Claim:
A ruthenium (II) compound of formula (I): wherein: R 1 is —CO 2 CH 3 ; R 2 , R 3 , R 4 , R 5 and R 6 independently represent H, alkyl, cycloalkyl, —CO 2 R′, aryl or alkylaryl, which latter two groups are optionally substituted on the aromatic ring; R′ represents alkyl, cycloalkyl, aryl or alkaryl; X is halo, H 2 O, (R′)(R″)SO, R′CO 2 − or (R′)(R″)C═O, where R″ represents alkyl, cycloalkyl, aryl or alkaryl; Y is a counterion; m is 0 or 1; q is 1, 2 or 3; C′ is C 1 to C 12 alkylene, optionally substituted in or on the alkylene chain, bound to two A groups; p is 0 or 1 and r is 1 when p is 0 and r is 2 when p is 1; and A and B are: each independently R 11 —CN, where R 11 represents alkyl or; or B is halo and A is a 4-substituted pyridine; or p is 0, A is NR 7 R 8 and B is NR 9 R 10 , wherein R 7 , R 8, R 9 and R 10 independently represent H, alkyl or cycloalkyl; and A and B are linked by an alkylene chain, optionally substituted in or on the alkylene chain; or p is 1, A is NR 7 and B is NR 9 R 10 , wherein R 7 , R 9 and R 10 are as previously defined, and A and B are linked by an alkylene chain, optionally substituted.