Charge-density analysis of the ground state of a photochromic 1,10-phenanthroline zinc(II) bis(thiolate) complex

Abstract

The charge density of the title compound was determined at 90 K, using a spherical crystal of 150 microm diameter. The proper treatment of the Zn atom in the pseudo-tetrahedral environment is considered in detail. A satisfactory refinement is only obtained when anharmonic Gram-Charlier parameters are included as variables in the refinement. A successful combined anharmonic/multipole refinement indicates a small polarization of the 4s shell in the anisotropic environment. One of the two toluenethiols is approximately pi-stacked with the phenanthroline ligand. A bond path is found connecting the two ligands. In addition the Zn-S bond to this ligand is slightly extended compared with the same bond to the second toluenethiol. A separate photocrystallographic and theoretical study indicates the long wavelength emission of the title compound to be due to a ligand-to-ligand charge transfer (LLCT) from a toluenethiol to the phenanthroline ligand. The charge-density results do not provide a basis for deciding which of the thiole ligands is the source of the transferred electron density. This result is in agreement with the theoretical calculations, which show comparable oscillator strengths for charge transfer from either of the ligands.

First experimental charge density study using a Bruker CMOS-type PHOTON 100 detector: the case of ammonium tetraoxalate dihydrate

“…Additionally, the refined anharmonic parameters appeared to be rather weakly correlated with multipolar parameters (the average correlation coefficient was equal to $ 0.5, the maximal was equal to 0.79 for the C 111 and Z -oriented dipole). These results are among many recent literature reports on this matter (Poulain et al, 2014;Herbst-Irmer et al, 2013;Zhurov et al, 2011;Scheins et al, 2010), where high-quality data allow for clear deconvolution of electron density and thermal motion features.…”

Multi-temperature study of potassium uridine-5′-monophosphate: electron density distribution and anharmonic motion modelling

“…The refined anharmonic parameters appeared to be rather weakly correlated with multipolar parameters. All these results are in line with many recent literature reports on this matter (Scheins et al, 2010;Zhurov et al, 2011;Herbst-Irmer et al, 2013;Poulain et al, 2014), where high-quality data allow for reliable deconvolution of electron density and thermal motion features. More details can be found in the supporting information.…”

“…0.8 Å À1 ), even though the first sign of its presence was found on the regular all-reflection map. The anharmonicity of the C7, C8, C9 and O9 atoms becomes apparent by the presence of the well known alternating positive-negative patterns around the atomic positions (Mallinson et al, 1988;Scheins et al, 2010;Herbst-Irmer et al, 2013;. Interestingly, all atoms seem to vibrate in a synchronous way, which indicates some anharmonic vibration of the whole uracil fragment.…”

Anharmonicity and isomorphic phase transition: a multi-temperature X-ray single-crystal and powder diffraction study of 1-(2′-aminophenyl)-2-methyl-4-nitroimidazole

“…Kuhs, 1988Kuhs, , 1992, their reliable separation from the static charge-density distribution parameters, disorder or librations was questioned (Mallinson et al, 1988;Restori & Schwarzenbach, 1996). Although Iversen et al (1999) distinguished anharmonic nuclear motions from static electron density features in a thorium complex structure using extremely high-resolution (1.7 Å À1 ) data from two very lowtemperature experiments (at 9 and 27 K), Henn et al (2010) were able to separate both contributions for lighter atoms (namely P atoms) at lower resolution (1.15 Å À1 ) at 100 K. Birkedal et al (2004) successfully refined the multipolar electron density of urea, while Scheins et al (2010) showed that ANMs are necessary for the correct description of the charge density of a Zn atom. Finally, Zhurov et al (2011) showed that neglecting ANMs in the case of hexahydro-1,3,5trinitro-1,3,5-triazine (RDX) results in unrealistic chargedensity deformation and Laplacian maps in the region of the nitro group.…”