A linear oligomer of benzaldehyde with 1,2,3-trihydroxybenzene was synthesised and characterized. The oligomer has a quinonic end group that leads to a solvatochromic property and interacts with a variety of amines. In aprotic medium the oligomer has two non-equivalent intra-molecular H-bonded quinonic states arising from keto-enol tautomerism, one having the carbonyl and olefinic group at the 1,4-disposition (X) whereas in the other the carbonyl and olefinic groups are at the 1,2-disposition (Y). Thus, in acetonitrile both forms exist and the X and Y states have their characteristic absorption maximum at 500 and 427 nm, respectively. In protic medium a highly ordered structure with the hydrophobic and hydrophilic part projecting apart produces a structure (Z) having inter-molecular hydrogen-bonding with solvent which has a characteristic absorption at 475 nm. Non-stoichiometric amounts of various primary, secondary and tertiary amines interact with the oligomer providing stability to either of the forms or generating an anion by which the absorption maximum changes. For example, the oligomer interacts with t-butylamine, and this interaction changes the absorption maximum to 566 nm. The solution on further treatment with mineral acid (HCl) gives a new absorption maximum at 475 nm with a distinct color change. The absorptions can be changed back and forth by alternate addition of hydrochloric acid and t-butylamine. However, the characteristic changes that take place in the optical spectra of the oligomer in acetonitrile with different amines are highly substrate-dependent. For example the amines like ammonia, ethylamine, iso-propylamine, n-butyl amine, t-butyl amine. ethylenediamine, and pyridine cause loss of absorption at 427 and 500 nm and lead to growth of new absorption at 566 nm whereas amines like benzidine, o-diaminobenzene, m-iodoaniline, m-nitroaniline, and p-hydroxyaniline enhance the original absorbance at 427 nm at the cost of absorption at 500 nm without leading to a new absorption. Some amines like 1-naphthylamine, 1,7-diaminonaphthalene, p-iodoaniline, and p-methoxyaniline increase the absorbances at 427 and 500 nm, whereas aniline, o-methylaniline, m-methylaniline, and diphenylamine do not significantly affect the spectra of the oligomer. The electrochemical study of the oligomer with 1,4-phenylenediamine shows that redox potentials of the bound state of the oligomer with 1,4-phenylenediamine shifts from the unbound state, for example, 1,4-phenylenediamine with the oligomer has two quasireversible couples at E-1/2 at 259 and 822 mV in contrast to the two reversible couples of free 1,4-phenylenediamine at 334 and 863 mV, respectively. (C) 2003 Elsevier Science B.V. All rights reserved.