Benzazolate complexes of Ni(II), [Ni(pbz)(tren)]ClO4 (pbz = 2-(2 '-hydroxyphenyl)-benzimidazole (pbm), 1, 2(2 '-hydroxyphenyl)-benzoxazole (pbx), 2, 2-(2 '-hydroxyphenyl)-benzothiazole (pbt), 3; tren = tris(2-aminoethyl)amine), are prepared by self -assembly reaction and structurally characterized. Theoretical DFT simulations are carried out to reproduce the features of their crystal structures and their spectroscopic and photophysic properties. The three complexes are moderately luminescent at room temperature both in acetonitrile solution and in the solid state, The simulations indicate that the absorption spectrum is dominated by two well-defined transitions, and the electronic density concentrates in three MOs around the benzazole ligands. The Stokes shifts of the emission spectra of complexes 1-3 are determined by optimizing the electronic excited state.