TY  - JOUR
A1  - Awad, Duha Jawad
A1  - Schilde, Uwe
A1  - Strauch, Peter
T1  - 4,4 '-Bis(tert-butyl)-2,2 '-bipyridinedichlorometal(II) - Synthesis, structure and EPR spectroscopy
JF  - Inorganica chimica acta : the international inorganic chemistry journal
N2  - Due to the better solubility of the 4,4'-substituted bipyridine ligand a series of 4,4'0-bis(tert-butyl)-2,2'-bipyridinedichlorometal(II) complexes, [M(tbbpy)Cl(2)], with M = Cu, Ni, Zn, Pd, Pt was synthesised and characterised. The blue copper complex 4,4'-bis(tert-butyl)-2,2'-bipyridinedichlorocopper(II) was isolated in two different polymorphic forms, as prisms 1 with a solvent inclusion and solvent-free as needles 2. Both structures were determined by X-ray structure analysis. They crystallise in the monoclinic space group P2(1)/c with four molecules in the unit cell, but with different unit cells and packing motifs. Whereas in the prisms 1, with the unit cell parameters a = 12.1613(12), b = 10.6363(7), c = 16.3074(15) angstrom, eta = 94.446(8)degrees, the packing is dominated by intra-and intermolecular hydrogen bonds, in the needles 2, with a = 7.738(1), b = 18. 333(2), c = 13.291(3) angstrom, beta = 97.512(15)degrees, only intramolecular hydrogen bonds appear and the complex molecules are arranged in columns which are stabilised by p-p-stacking interactions. In both complexes the copper has a tetrahedrally distorted coordination sphere. These copper complexes were also studied by EPR spectroscopy in solution, as frozen glass and diamagnetically diluted powder with the analogue [Pd(tbbpy)Cl(2)] as host lattice.
KW  - 4,4 '-Bis(tert-butyl)-2,2 '-bipyridine
KW  - X-ray structure
KW  - EPR
KW  - Copper(II)
KW  - Transition metals
Y1  - 2011
U6  - https://doi.org/10.1016/j.ica.2010.08.035
SN  - 0020-1693
VL  - 365
IS  - 1
SP  - 127
EP  - 132
PB  - Elsevier
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Hoffmann, Katrin
A1  - Dietzel, Birgit
A1  - Schulz, Burkhard
A1  - Reck, Guenter
A1  - Hoffmann, Angelika
A1  - Orgzall, Ingo
A1  - Resch-Genger, Ute
A1  - Emmerling, Franziska
T1  - Combined structural and fluorescence studies of methyl-substituted 2,5-diphenyl-1,3,4-oxadiazoles - Relation between electronic properties and packing motifs
JF  - Journal of molecular structure
N2  - Prerequisite for the rational design of functional organic materials with tailor-made electronic properties is the knowledge of the structure-property relationship for the specific class of molecules under consideration. This encouraged us to systematically study the influence of the molecular structure and substitution pattern of aromatically substituted 1,3,4-oxadiazoles on the electronic properties and packing motifs of these molecules and on the interplay of these factors. For this purpose, seven diphenyl-oxadiazoles equipped with methyl substituents in the ortho- and meta-position(s) were synthesized and characterized. Absorption and fluorescence spectra in solution served here as tools to monitor substitution-induced changes in the electronic properties of the individual molecules whereas X-ray and optical measurements in the solid state provided information on the interplay of electronic and packing effects. In solution, the spectral position of the absorption maximum, the size of Stokes shift, and the fluorescence quantum yield are considerably affected by ortho-substitution in three or four ortho-positions. This results in blue shifted absorption bands, increased Stokes shifts, and reduced fluorescence quantum yields whereas the spectral position and vibrational structure of the emission bands remain more or less unaffected. In the crystalline state, however, the spectral position and shape of the emission bands display a strong dependence on the molecular structure and/or packing motifs that seem to control the amount of dye-dye-interactions. These observations reveal the limited value of commonly reported absorption and fluorescence measurements in solution for a straightforward comparison of spectroscopic results with single X-ray crystallography. This underlines the importance of solid state spectroscopic studies for a better understanding of the interplay of electronic effects and molecular order.
KW  - Diphenyl-oxadiazoles
KW  - X-ray structure
KW  - Packing motif
KW  - Optical properties
KW  - Fluorescence quantum yield
Y1  - 2011
U6  - https://doi.org/10.1016/j.molstruc.2010.11.071
SN  - 0022-2860
VL  - 988
IS  - 1-3
SP  - 35
EP  - 46
PB  - Elsevier
CY  - Amsterdam
ER  -