| abstract |
Compounds of the formula n n nwherein M is either (1) a metal ion having a positive charge of +y wherein y is an integer which is at least 2, said metal ion being capable of forming a compound with at least two n n nchromogen moieties, or (2) a metal-containing moiety capable of forming a compound with at least two n n nchromogen moieties, z is an integer representing the number of n n nchromogen moieties associated with the metal and is at least 2, and R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , a, b, c, d, Y, Q − , A, and CA are as defined herein. |