New symmetrical and unsymmetrical near‐infrared absorbing ketocyanine‐type dyes are synthesized and their optical characterization is done. The relationships between their structure and optical properties are discussed. The synthesized ketocyanine dyes show a positive solvatochromism and are poorly fluorescent. A new procedure for the preparation of N ,N ,N ′,N ′‐ tetramethylvinamidinium perchlorate