New cyanine dyes derived from tetrazolo[5,1-a]isoindoles

The investigation of the acylation reaction of 1-methyltetrazolo[5,1-a]isoindole with acyl chlorides gave rise to two series of derivatives. 5-Acyl-1-methyltetrazolo[5,1-a]isoindoles and a new type of tetrazoloisoindole based monomethinecyanines were isolated. Their structure was confirmed by X-ray diffraction analysis. A mechanism of the formation of these new dyes is proposed. This reaction permit to introduce easily various alkyl, aryl or heteroaryl substituents on the central methine carbon.