We discuss the results of correlated quantum-chemical calculations aimed at
addressing the way intermolecular interactions influence the absorption an
d emission properties of conjugated chains. The nature of the lowest excite
d states in molecular aggregates is discussed and a special emphasis is giv
en to the effect of chain length and relative positions of the interacting
units on the calculated properties. Strategies are suggested that could sig
nificantly reduce luminescence quenching in light-emitting devices. (C) 200
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