Abstract
Cyclometalated platinum(II) complexes [Pt(ppy)Cl(CNAr)] (ppy = 2-phenylpyridinato-C(2),N; Ar = C(6)H(4)-2-I 1, C(6)H(4)-4-I 2, C(6)H(3)-2-F-4-I 3, and C(6)H(3)-2,4-I(2) 4) bearing ancillary isocyanide ligands were obtained by the bridge-splitting reaction between the dimer [Pt(ppy)(μ-Cl)](2) and 2 equiv any one of the corresponding CNAr. Complex 2 was crystallized in two polymorphic forms, namely, 2 (I) and 2 (II), exhibiting green (emission quantum yield of 0.5%) and orange (emission quantum yield of 12%) phosphorescence, respectively. Structure-directing non-covalent contacts in these polymorphs were verified by a combination of experimental (X-ray diffraction) and theoretical methods (NCIplot analysis, combined electron localization function (ELF), and Bader quantum theory of atoms in molecules (QTAIM analysis)). A noticeable difference in the spectrum of non-covalent interactions of 2 (I) and 2 (II) is seen in the Pt···Pt interactions in 2 (II) and absence of these metallophilic contacts in 2 (I). The other solid luminophores, namely, 1, 3 (I-II), 4, and 4·CHCl(3), exhibit green luminescence; their structures include intermolecular C-I···Cl-Pt halogen bonds as the structure-directing interactions. Crystals of 1, 2 (I), 3 (I), 3 (II), 4, and 4·CHCl(3) demonstrated a reversible mechanochromic color change achieved by mechanical grinding (green to orange) and solvent adsorption (orange to green).