DMF Solvent Molecules Research Articles

Optical Absorption Spectroscopy of Strongly Disordered J-Aggregates: Control of Off-Diagonal Disorder

It was shown that the low-frequency edge of the exciton absorption band of J-aggregates of l-methyl-l′-octadecyl-2,2′-cyanine iodide (analogue of PIC) experiences a change from Gaussian to Lorentzian in frozen, binary DMF-H2O solution, upon decrease of water concentration. In a Langmuir-Blodgett film, the shape of the low-frequency edge of exciton absorption band was neither Gaussian nor Lorentzian, in contrast. A model of diagonal and off-diagonal disorder in the molecular chains is proposed to explain the observed band shapes, based on selective solvation of amphiphilic molecules by water and DMF solvent molecules.

Synthesis and structure of didysprosium complexes with a tetraketone

Two novel didysprosium (Dy 2) complexes of 1,5-bis(1′-phenyl-3′-methyl-5′-pyrazolone-4′)-1,5-pentanedione (H 2L), Dy 2L 3·2H 2O and Dy 2L 3·5DMF (DMF = dimethylformamide), have been synthesized. The crystal structure of Dy 2L 3·5DMF was determined by X-ray diffraction. Crystals are triclinic, space group P1̄, with a = 16.99(1), b = 17.970(9), c = 18.28(1) Å, α = 110.36(4), β = 101.47(6), γ = 111.11(5)°, V = 4533(9) Å 3, M r = 2017.91, Z = 2, D x = 1.48 g cm −3, μ = 17.22 cm −1, F(000) = 2056, R = 0.074 with 3804 reflections used in the refinement. In the complex, each L bonds two dysprosium atoms with its two β-diketone groups. Two DMF solvent molecules bond to each dysprosium ion. The coordination number of the two dysprosium ions is eight. The eight oxygen atoms around the dysprosium ion make up a distorted square antiprism coordination polyhedron. The resonance structures of coordinated β-diketonates are also discussed. Different lanthanide ions may stabilize the specific structure.

SYNTHESIS AND STRUCTURE OF DINUCLEAR COMPLEXES OF TERBIUM(III) WITH 4-ACETALBISPYRAZOLONE

Abstract Two novel dinuclear complexes of terbium(III) with 1,5-bis(1′-phenyl-3′-methyl-5′-pyrazolone-4′)-1,5-pentanedione (H2L), Tb2L3·6H2), Tb2L3·SDMF, have been synthesized. The crystal structure of Tb2L3 · 5DMF was determined by X-ray diffraction methods. Crystals are triclinic, space group P 1 with α = 16.957(5), b = 17.877(7), c = 18.269(2)A, α = 110.35(2), β = 101.29(2), γ = 111.00(2)°, V = 4511(6)A3, Mr = 2010.76, Z = 2, Dx = 1.48g cm−3, μ = 16.45 cm−1, F(000) = 2,052, R = 0.058 with 6574 reflections used in refinement. In the complex, L acts as a bridging ligand and bonds two terbium atoms with its two β-diketone groups. Each terbium ion bonds to two DMF solvent molecules. The coordination number of the two terbium ions is eight. The eight oxygen atoms around the terbium make a distorted square antiprismatic coordination polyhedron.

Synthesis and characterization of copper(II) complexes with a tridentate schiff base ligand derived from 5-chloro-2-hydroxyacetophenone and salicylhydrazide. X-ray structure of copper(II) (5-chloro-2-hydroxyacetophenone-salicylhydrazide) dimethylformamide

Two copper(II) complexes with the Schiff base derived from the condensation of 5-chloro-2- hydroxyacetophenone and salicylhydrazide have been prepared and characterized by means of IR, electronic and EPR spectroscopies and magnetic measurements. For Cu(II) (5-chloro-2-hydroxyacetophenonesalicylhydrazide) dimethylformamide, Cu(5Cl-OHA-SHZ) DMF, obtained by recrystallizing the anhydrous complex Cu(5Cl-OHA-SHZ) from dimethylformamide solution, the crystal structure was also determined. Crystals of Cu(5Cl-OHA-SHZ) DMF are triclinic, space group P 1 , with two molecules in a unit cell of dimensions: a = 8.012(2), b = 8.359(2), c = 13.906(1) Å, α = 88.80(1), β = 88.48(1), γ = 82.01(1)°, and V= 918(1) Å 3. Refinement by full-matrix least-squares gave a final R w = 0.058. In the mononuclear molecule the copper atom is bonded to three ONO donor atoms from the Schiff base ligand and to an oxygen atom from the DMF solvent molecule in a highly distorted square planar geometry. The EPR spectrum of this DMF coordinated complex has been interpreted in terms of the great deviation of the coordination geometry from the idealized square planar one. Cu(5Cl-OHA-SHZ) DMF was found to be a normal paramagnet. Variable temperature magnetic studies on the anhydrous compound suggest a dimeric structure with strong anti-ferromagnetic interactions (2 J = −439 cm −1). The IR spectra are discussed in comparison with that of the free ligand.