M···π-conjugated complexes: simple materials with dramatic NLO features (M = Li, Na, K, and π = butadiene, cyclobutadiene, hexatriene, benzene).

Theoretical investigation of linear and nonlinear optical (NLO) properties in simple complexes consist of alkali metals and π-conjugated systems have been studied at MP2/6-311++G(2d,2p) computational level. Lithium, sodium, and potassium as alkali metals were chosen for interaction with some non-aromatic, aromatic and anti-aromatic systems. For better comparison of results, the π-systems were chosen with the same carbon number: butadiene as a non-aromatic in comparison with cyclobutadiene as an anti-aromatic and hexatriene as a non-aromatic in comparison with benzene as an aromatic system. Results revealed that gap energy of studied π-systems was decreased under the interacting with alkali metals. Furthermore all designed complexes were shown very good results in average polarizability (<italic>α</italic>) and first hyperpolarizability (<italic>β</italic>0) parameters. So these very simple dimer complexes could be introduced as promising innovative nonlinear optical materials. [ABSTRACT FROM AUTHOR]