Synthesis, structural characterization, and luminescence properties of mono- and di-nuclear platinum(II) complexes containing 2-(2-pyridyl)-benzimidazole

Abstract

The starting complex [Pt(Me)(DMSO)(pbz)], (1, (pbz = 2-(2pyridyl)benzimidazolate) was prepared by a known method using the 1 reaction of [Pt(Me) 2 (DMSO) 2 ], A, with Hpbz at room temperature. Reaction of 1 with an equivalent of a phosphine ligand gave the neutral mononuclear complexes [Pt(Me)(L)(pbz)], )] ( 2, (L = PPh 3 ) or and 3, (L =PPh 2 Me). Reaction of 1 with 0.5 equivalent of the linear diphosphine 1,1'-bis(diphenylphosphino)acetylene (dppac) gave the binuclear complex [Pt 2 (Me) 2 (μ-dppac)(pbz) 2 ], 4. All Each the complexes were was fully characterized by NMR spectroscopy, X-ray crystallography and mass spectrometry. The photophysical properties of the complexes were investigated in under different conditions and interpretation was, supported by TD-DFT calculations. The low-lying transitions in the absorption and emission spectra were assigned as having LLCT/MLCT (ligand to ligand charge transfer/metal-to-ligand charge transfer) character. We also describe the luminescence properties of [Pt(Me)(PPh 3 ) (ppy)], 7, and [Pt(Me)(PPh 2 Me)(ppy)], 8, (ppy is 2-phenylpyridinate), the (N^C  ) analogues of 2 and 3.

Selectivity and competition between N–H and C–H bond activation using an organoplatinum (II) complex

“…The compound 2-(2 0 -pyridyl) benzimidazole (Hpbz) was purchased from commercial sources. The complexes (PtMe 2 (DMSO) 2 ), 1, [46] and (PtMe(pbz-κ 2 -N,N)(DMSO)], 2, 47,48 were prepared as reported in the literature, and the isolated compounds were characterized by comparing their NMR and UV-vis spectra with those of previously prepared materials (see Figures S1 and S2).…”

“…For DFT calculations, the B3LYP level has been proven to be a suitable method for transition-metal complexes. [54][55][56] For example, to estimate the suitability of the DFT/B3LYP level of calculations used in the present work, complex 2 that was structurally characterized by X-ray crystallography [47] is selected as a standard example. Figure 1 shows overlay of the computed structure of complex 2, with the X-ray structure of 2.…”

“…Complex 2 was easily synthesized by reaction of Hpbz with complex 1 in common organic solvents such as chloroform or acetone and characterized by comparing its 1 H NMR spectrum with that of authentic samples. [47] Reaction of complex 1 with Hpbz ligand under 1:1 stoichiometric condition was monitored by 1 H NMR spectroscopy as shown in Figure 2. Immediately after the addition of Hpbz to a solution of complex 1, a mixture of complex 1 and product 2 was detected.…”

“…Overlay of the energetically favored computed structure of complex 2, with the X-ray structure of 2. [47] Selected bond distances (Å) and angles ( ) are also shown The reaction of complex 1 with Hpbz in chloroform was examined spectrophotometrically with the aim of obtaining kinetics of DMSO substitution, N-H activation and C-H bond formation during the process. The reaction was followed by UV-vis monitoring the change in absorbance at the indicated wavelength.…”

“…In fact, the reaction of 1 with Hpbz leads to formation of methane and (PtMe(pbz-κ 2 -N,N)(DMSO)), 2. [47] Density functional theory (DFT) calculations are used to quantify the energetics of the competing N-H and C-H bond activation pathways.…”