C CHEMISTRY; METALLURGY
C09 DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
C09B ORGANIC DYES OR CLOSELY-RELATED COMPOUNDS FOR PRODUCING DYES; , e.g. PIGMENTS; MORDANTS; LAKES
C09B23/00 Methine or polymethine dyes, e.g. cyanine dyes
C09B23/16 the polymethine chain containing hetero atoms
C09B23/162 only nitrogen atoms
C09B23/166 containing two or more nitrogen atoms