Structural properties of platinum(II) biphenyl complexes containing 1,10-phenanthroline derivatives

• X-ray structures deviate from square planar into two types of structures, X and bowed (B) forms.
• X and B forms exhibit circular dichroism in the solid state.
• Circular dichroism spectra can be correlated with optimized structures determined by DFT calculations.
• Heteronuclear interactions are observed by NMR between 195Pt and ring protons of phenanthroline and biphenyl ligand.
• A Hammett sigma correlation exists with the most downfield proton resonance.

Seven platinum(II) complexes formulated as Pt(bph)L, where bph is the 2,2′-biphenyl dianion and L = 4-methyl-1,10-phenanthroline (4-Mephen), 5-methyl-1,10-phenanthroline (5-Mephen), 5-chloro-1,10-phenanthroline (5-Clphen), 5,6-dimethyl-1,10-phenanthroline (5,6-Me2phen), 4,7-dimethyl-1,10-phenanthroline (4,7-Me2phen), 4,7-diphenyl-1,10-phenanthroline (4,7-Ph2phen) and 3,4,7,8-tetramethyl-1,10-phenanthroline (3,4,7,8-Me4phen) are reported. Protons attached to the phen ligand resonate downfield from those attached to the bph ligand and two proton signals are split by interaction with 195Pt. Pt(bph)(3,4,7,8-Me4phen), Pt(bph)(4,7-Me2phen), Pt(bph)(5,6-Me2phen), Pt(bph)(4,7-Ph2phen) and Pt(bph)(5-Mephen) crystallize in the space groups Pna21, P21/n, P21/c, P − 1 and Pca21, respectively. The structures of the complexes deviate from true planarity and divide themselves into two groups where the bph and phen ligands cross in an X configuration or bow out in a butterfly (B) configuration. Circular dichroism revealed two different spectra with respect to the X and B configurations.