THE 1ST DETERMINATION OF THE ENERGY DIFFERENCE BETWEEN SOLID-STATE CONFORMERS BY X-RAY-DIFFRACTION .1. THE CRYSTAL-STRUCTURE OF THE PSEUDO-JAHN-TELLER COMPLEX (NITRITO)BIS(2,2'-BIPYRIDYL)COPPER(II) NITRATE AT 20-K, 100-K, 165-K, AND 296-K AND OF ITS ISOSTRUCTURAL ZINC(II) ANALOG AT 295-K .2. THE POSSIBILITY OF USING X-RAY-DIFFRACTION TO CHARACTERIZE ADIABATIC POTENTIAL-ENERGY SURFACES AND RELATIVE LIGAND STRENGTHSI
Academic Article
Overview
Identity
Additional Document Info
Other
View All
Overview
abstract
The first determination of the energy difference (A) between solid-state conformers by X-ray diffraction is reported for the pseudo-Jahn-Teller complex [Cu(bpy)2(0N0)]N03; X-ray data were collected at 20, 100, 165, and 296 K. By invoking an adiabatic potential energy surface consisting of two nonequivalent ground-state minima and by applying Boltzmann statistics to it, AE could be determined (77 cm-1) from the temperature variation of the structure of the CuN402chromophore. The crystal structure of the isostructural and orbitally nondegenerate [Zn(bpy)2(0N0)]N03complex was also determined, at 295 K. Both complexes crystallize in the monoclinic space group Plxfn with Z = 4. The unit cell parameters are a = 11.067 (2) k,b = 12.014 (3) A, c = 14.855 (7) A, (3 = 100.01 (3), V= 1945 (1) A34, dcM= 1.653 gem3, T = 20 K;a = 11.168(4)A,b= 11.945 (5) k,c = 14.909 (6) k, (3 = 99.32 (3), V= 1962 (1) A3, calcd= 1.638 gem3, T= 100 K;a = 11.217(2)A,6 = 1 1.936(5)A,c = 14.969(3)A,0 = 99.14(2),1979(2)A3,dcM= 1.624 gcm3, 7= 165 K; a = 11.225 (2) A, b = 12.035 (5) A, c = 15.109 (5) A, 0 = 99.55 (2), V = 2013 (2) A3, calcd= 1.597 g cm3, T = 296 K for [Cu(bpy)2(ONO)]N03and a = 11.292 (3) A, b = 11.962 (4) A, c = 15.384 (5) A, 0 = 101.16 (2), V = 2039 (1) A3, 22< 7=296 K) reflections for [Cu(bpy)2(0N0)]N03and 2185 (> 3a7 = 295 K) for [Zn(bpy)2(ONO)]N03gave the following RuR2, and GOF (goodness-of-fit) values: 0.037, 0.028, 1.44; 0.044, 0.032, 1.39; 0.046, 0.076, 2.35; 0.046, 0.053, 1.30; and 0.036, 0.044, 2.90, respectively. The possibility of using low-temperature X-ray diffraction and ESR spectroscopy to determine the energies of the vibronically coupled ground and first-excited electronic states in [Cu(bpy or phen)2(OXO)] Y complexes and to obtain the relative ligand strengths of various OXO groups (OXO-- CH3C02, N02, etc.) is also discussed. 1987, American Chemical Society. All rights reserved.
