Terpyridine Zn(ii), Ru(iii) and Ir(iii) complexes as new asymmetric chromophores for nonlinear optics: first evidence for a shift from positive to negative value of the quadratic hyperpolarizability of a ligand carrying an electron donor substituent upon coordination to different metal centres

The synthesis of 4'-(C6H4-p-NBU2)-2,2':6',2" -terpyridine and the strongly enhanced second-order NLO response of its Zn(II), Ru(III) and Ir(III)complexes are reported, evidencing for the first time a shift from positive to negative value of the ligand quadratic hyperpolarizability by varying the nature of the metal centre. .