An effective method has been developed for synthesis of neutral merocyanine dye 4 from (4-nitrophenyl)malondialdehyde. Merocyanine 4 was used as a basic building block for preparation of unsymmetric cyanine dyes 9 and 10, both derived from the same aromatic malondialdehyde.
With the cyanine 10, pH-dependent affinity to DNA has been studied. Unsymmetric cyanine dye 10 has been compared with symmetric dye 8.
The corresponding binding constants (K) have been calculated for various pH.