NMR studies of the reaction between amino-phenylene vinylene thiophene and tetracyanoethylene

Amino tricyanovinyl thiophene chromophores (A-TCVT) are prepared by a substitution reaction of amino-phenylene vinylene thiophene (A-PVT) with tetracyanoethylene (TCNE). This reaction does not occur directly. The vinylene double bond in the PVT unit first reacts rapidly with TCNE to form a [2+2] cycloaddition product. It is then reverted to PVT unit prior to the subsequent substitution at 50 °C. This reversible cycloaddition converts the cis-isomer of PVT units into the trans-counterparts, thus the final TCNE substituted products can be expected for a better performance as non-linear optical materials.

PVT groups in polymers and in a model compound react with TCNE quickly in DMF at room temperature to form [2+2] cycloaddition products, which convert to substitution products at 50 °C.