scholarly journals Synthesis, Structural Features and Physical Properties of a Family of Triply Bridged Dinuclear 3d-4f Complexes

2021 ◽  
Vol 7 (2) ◽  
pp. 22
Author(s):  
Itziar Oyarzabal ◽  
Estitxu Echenique-Errandonea ◽  
Eider San Sebastián ◽  
Antonio Rodríguez-Diéguez ◽  
José Manuel Seco ◽  
...  
Keyword(s):  
Metal Ions ◽  
Density Functional ◽  
Magnetic Measurements ◽  
Theoretical Calculations ◽  
Exchange Interactions ◽  
Transition Metal Ions ◽  
Structural Features ◽  
Coupling Constants ◽  
Metallic Ions ◽  
Magnetic Exchange

New dinuclear MII-LnIII complexes of general formulas [Cu(µ-L)(µ-OAc)Ln(NO3)2]·CH3CN·H2O (LnIII = Gd (1), Tb (2), Dy (3) and Er (4)), [Ni(CH3CN)(µ-L)(µ-OAc)Ln(NO3)2]·CH3CN (LnIII = Nd (5), Gd (6), Tb (7), Dy (8), Er (9) and Y (10)) and [Co(CH3CN)(µ-L)(µ-OAc)Ln(NO3)2]·CH3CN (LnIII = Gd (11), Tb (12), Dy (13), Er (14) and Y (15)) were prepared from the compartmental ligand N,N′-dimethyl-N,N′-bis(2-hydroxy-3-formyl-5-bromo-benzyl)ethylenediamine (H2L). In all these complexes, the transition metal ions occupy the internal N2O2 coordination site of the ligand, whereas the LnIII ions lie in the O4 external site. Both metallic ions are connected by an acetate bridge, giving rise to triple mixed diphenoxido/acetate bridged MIILnIII compounds. Direct current (dc) magnetic measurements allow the study of the magnetic exchange interactions between the 3d and 4f metal ions, which is supported by density functional theory (DFT) theoretical calculations for the GdIII-based counterparts. Due to the weak ferromagnetic exchange coupling constants obtained both experimentally and theoretically, the magneto-thermal properties of the less anisotropic systems (compounds 1 and 6) are also studied. Alternating current (ac)magnetic measurements reveal the occurrence of slight frequency dependency of the out-of-phase signal for complexes 8, 9 and 13, while complex 15 displays well-defined maximums below ~6 K.

MAGNETIC EXCHANGE IN POLYNUCLEAR TRANSITION METAL SYSTEM: AB INITIO CASPT2 AND DENSITY FUNCTIONAL THEORY STUDY ON TRIANGULAR COPPER(II) COMPLEXES

2006 ◽  
Vol 05 (spec01) ◽  
pp. 501-514 ◽  
Author(s):  
HAIYAN WEI ◽  
ZHIDA CHEN
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
Density Functional ◽  
Magnetic Coupling ◽  
Exchange Interactions ◽  
Coupling Constants ◽  
Magnetic Exchange ◽  
Functional Theory ◽  
Symmetry Approach ◽  
Spin Electronic

The magnetic exchange interactions for five representative triangular Copper(II) complexes: antiferromagnetic Cu 3( TiPB )6 (1), [ Cu 3(μ3- OH )( aaat )3( H 2 O )3]2+ (2), [ PPN ]2 [ Cu 3(μ3- O )(μ- pz )3 Cl 3] (3), [ PPN ][ Cu 3(μ3- OH )(μ- pz )3 Cl 3] (4) and ferromagnetic [ Cu 3(2- CH 3 C 6 H 4 CO 2)4{( C 2 H 5)2 NC 2 H 4 O }2 H 2 O ] (5) are investigated by using density functional theory combined with broken-symmetry approach (DFT-BS) and ab initio CASPT2 method. Our calculated results show that DFT-BS has remarkable dependence on the particular chosen XC functionals and is system-dependent, while the calculations at CASPT2 level of theory are able to give the accurate magnetic coupling constants. Qualitatively, the two theoretical methods reproduce consistently the linear correlation between the magnetic coupling constants and the departure of the (μ3- O ) oxygen atom from the { Cu3 } plane in the complexes (3) and (4). Spin population analyses reveal that the DFT-BS method overestimates the spin electronic delocalization from the Cu(II) center to the bridging ligands.

Magnetic exchange interactions and band gap bowing in NixMg1−xO (0.0 ≤ x ≤ 1.0): A GGA+U density functional study

2019 ◽  
Vol 126 (23) ◽  
pp. 233904
Author(s):  
Sayandeep Ghosh ◽  
Suchit Kumar Jena ◽  
Pankaj Kumar Mishra ◽  
Mohindar S. Seehra ◽  
Subhash Thota
Keyword(s):  
Band Gap ◽  
Density Functional ◽  
Exchange Interactions ◽  
Functional Study ◽  
Magnetic Exchange ◽  
Density Functional Study

scholarly journals Estudo do tautomerismo ceto-enólico da 7-epi-clusianona através de cálculos teóricos de deslocamentos químicos de RMN

2020 ◽  
Author(s):  
Ana Carolina Ferreira de Albuquerque ◽  
José Walkimar de Mesquita Carneiro ◽  
Fernando Martins dos Santos Junior
Keyword(s):  
Natural Products ◽  
Structural Characterization ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Spectroscopic Techniques ◽  
Chemical Structures ◽  
Nmr Parameters

The properties of natural products, including their biological and pharmacological activities, are directly correlated with their chemical structures. Thus, a correct structural characterization of these compounds is a crucial step to the understanding of their biological activities. However, despite the recent advances in spectroscopic techniques, structural studies of natural products can be challenging. This way, theoretical calculations of Nuclear Magnetic Resonance (NMR) parameters (such as chemical shifts and coupling constants) have proven to be a powerful and low-cost tool for the aid to experimental techniques traditionally used for the structural characterization of natural products. One of the several applications of quantum-mechanical calculations of NMR parameters is the study of tautomerism. Since chemical shifts are sensitive to the tautomeric equilibrium, this technique can provide crucial informations. In this work, it was applied a protocol for theoretical calculations of ¹³C chemical shifts in order to study the tautomerism of the natural product 7-epi-clusianone, isolated from Rheedia gardneriana. This protocol consists in a Monte Carlo conformational search, followed by geometry optimization and shielding tensors calculations, both using a density functional level of theory. After comparison of theoretical and experimental data, it was possible to confirm the two tautomers present in equilibrium in the experimental solution. Furthermore, this study highlights how this theoretical protocol can be an effective method in identifying the preferred tautomeric form in solution.

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