Enhancement of charge-transfer complex formation between 1,4-dimethyl-naphthalene and p-chloranil during the sol–gel reaction of tetraethyl orthosilicate

The absorption spectra of mixed solutions composed of 1,4-dimethyl-naphthalene (DMN) and p-chloranil (pC) in tetraethyl orthosilicate dispersions during a sol–gel reaction catalyzed by HCl at room temperature have been observed as a function of time. Just after preparing the solution, the absorption band of the charge-transfer (CT) absorption at around 535 nm due to the CT complex formation between pC and DMN was barely visible. As the sol–gel reaction proceeded, the intensity of the CT band increased with reaction time. This increase in the CT absorption band was highly enhanced after the gelation and stopped after ca. 100 days.