Tetrahedral molecular geometry

About: Tetrahedral molecular geometry is a research topic. Over the lifetime, 1795 publications have been published within this topic receiving 30706 citations.

Examination of cobalt, nickel, copper and zinc( ii ) complex geometry and binding affinity in aqueous media using simple pyridylsulfonamide ligands

Abstract: The sixteen neutral ML2 complexes of Co, Ni, Cu and Zn(II) with the p-toluenesulfonamide and trifluoromethylsulfonamide derivatives of 2-aminomethylpyridine (L1, L2) and its 6-Me homologue (L3, L4) have been characterised by low temperature X-ray crystallography (100–120 K). Complexes of Co and Zn invariantly adopted a distorted tetrahedral geometry and whilst Cu(II) complexes of L2, L3 and L4 also took up a distorted tetrahedral geometry, that with L1 was square planar. A database survey of the distortion from limiting tetrahedral/square planar geometry has been carried out, aided by a simple geometric analysis. The trifluoromethylsulfonamide ligands (L2 and L3) were less basic, e.g. log K1 7.51(3) for L2vs. 12.23(6) for L1 (80% MeOH/H2O) and afforded a weaker ligand field, exemplified by the position of the visible d–d transition in Cu(II) complexes and the ease of reduction of the Cu(II) centre: E1//2 values (MeCN vs. Ag/AgCl) are −430, −137, +55 and −240 mV for Cu(L1)2, Cu(L2)2, Cu(L3)2 and Cu(L4)2. Ligand protonation and stepwise formation constants have been measured for L1–L3 and derived species distribution diagrams reveal that for complexes with L2 and L3, the predominant species present at pH 7.4 when zinc was in the nanomolar range was ZnL2.

Relation between structure and spectra of pseudo-tetrahedral copper(II) complexes. Crystal structure of bis(di-2-pyridylamido)copper(II)

Abstract: The copper(II) complex of the deprotonated form of di-2-pyridylamine has been prepared by treating the ligand with freshly prepared copper(II) hydroxide, and the crystal structure determined. Crystal data: Monoclinic, space group C2/c, a= 14.691(6), b= 12.256(9), c= 11.945(2)A, β= 124.24(3)°, and Z= 4. The final R value was 0.039 for 1 052 independent, observed reflections. The copper atom environment is pseudo-tetrahedral with a dihedral angle of 58.8° between the two CuN2 ligand planes. It is demonstrated that the observed molecular structure and the ligand field spectra in the literature are in good agreement. The extent of distortion from pure tetrahedral geometry in a series of related copper bis(bidentate ligand) complexes, as estimated from ligand-field spectra, correlates very well with the observed crystallographic dihedral angle values. This structural result is now available for calibration of the electronic and e.s.r. spectral data for small-molecule pseudo-tetrahedral copper(II) complexes and the presumed four-co-ordinated Type I ‘blue’ copper protein sites.

Collision‐induced absorption in mixtures of symmetrical linear and tetrahedral molecules: Methane–nitrogen

Abstract: The far infrared absorption of a CH4-N2 mixture was measured at 297, 195, and 162 K from 30 to 650/cm. The spectral invariants gamma1 and alpha1, proportional, respectively, to the zeroth and first spectral moments, due to bimolecular collisions between CH4 and N2 were obtained from these data and compared with theoretical values. The theory for collision-induced dipoles between a tetrahedral and a diatomic or symmetrical linear molecule includes contributions not previously considered. Whereas the theoretical values of gamma1 are only somewhat greater than experiment at all temperatures, the theoretical values of alpha1 are significantly lower than the experimental values. From the theoretical spectral moments for the various induced dipole components, the parameters of the BC shape were computed, and theoretical spectra were constructed. Good agreement was obtained at the lower frequencies, but with increasing frequencies the theoretical spectra were increasingly less intense than the experimental spectra. Although the accuracy of the theoretical results may suffer from the lack of a reliable potential function, it does not appear that this high frequency discrepancy can be removed by any conceivable modification in the potential.