Spin Symmetry Requirements in Density Functional Theory: The Proper Way to Predict Magnetic Coupling Constants in Molecules and Solids

Magnetic coupling constants J for the complete structures of [ Gd(capro) 2( H 2 O )4 Cr(CN) 6]• H 2 O (capro represents caprolactam) (a) and trans-[ Fe(CN) 4(μ- CN )2 Gd ( H 2 O )4 (bpy) ]•4 H 2 O •1.5 bpy (b) have been calculated using hybrid density functional theory (DFT) B3LYP combined with a modified broken symmetry approach (BS). The calculated J value of -0.24 cm-1 for a is very close to the experimental -0.33 cm-1. They both show the antiferromagnetic interaction between Gd(III) and Cr(III) . For b, although the sign of the calculated J value of 4.24 cm-1 is different from that of the experimental -0.38 cm-1, the two values both show the weak magnetic coupling interaction between Gd(III) and Fe(III) . The spin density distributions are discussed on the basis of Mulliken population analysis. For complexes a and b, both transition metal ( Fe(III) or Cr(III) ) and rare earth Gd(III) display a spin polarization effect on the surrounding atoms, where a counteraction of the opposite polarization effects leads to a low spin density on the bridging ligand C1N1 . For the compounds Gd(III) - Cr(III) (a) and Gd(III) - Fe(III) (b) in the HS states, Cr(III) has stronger spin polarization influence on the bridging atoms than Fe(III) even causing the positive spin population on the bridging atom N1 .

Download Full-text

Magnetic coupling constants for MnO as calculated using hybrid density functional theory

Chemical Physics Letters ◽

10.1016/j.cplett.2017.10.027 ◽

2017 ◽

Vol 690 ◽

pp. 47-53 ◽

Cited By ~ 3

Author(s):

Andrew J. Logsdail ◽

Christopher A. Downing ◽

C. Richard A. Catlow ◽

Alexey A. Sokol

Keyword(s):

Density Functional Theory ◽

Density Functional ◽

Magnetic Coupling ◽

Coupling Constants ◽

Hybrid Density Functional Theory ◽

Functional Theory ◽

Hybrid Density Functional

Download Full-text

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

Journal of Theoretical and Computational Chemistry ◽

10.1142/s0219633606002428 ◽

2006 ◽

Vol 05 (spec01) ◽

pp. 501-514 ◽

Cited By ~ 3

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.

Download Full-text

Assessing the Calculation of Exchange Coupling Constants and Spin Crossover Gaps Using the Approximate Projection Model to Improve Density Function Calculations

10.26434/chemrxiv.7976474.v2 ◽

2019 ◽

Author(s):

Xianghai Sheng ◽

Lee Thompson ◽

Hrant Hratchian

Keyword(s):

Density Functional Theory ◽

Exchange Coupling ◽

Density Functional ◽

Spin Crossover ◽

Coupling Constants ◽

Spin Projection ◽

Coupling Constant ◽

Projection Model ◽

Functional Theory

This work evaluates the quality of exchange coupling constant and spin crossover gap calculations using density functional theory corrected by the Approximate Projection model. Results show that improvements using the Approximate Projection model range from modest to significant. This study demonstrates that, at least for the class of systems examined here, spin-projection generally improves the quality of density functional theory calculations of J-coupling constants and spin crossover gaps. Furthermore, it is shown that spin-projection can be important for both geometry optimization and energy evaluations. The Approximate Project model provides an affordable and practical approach for effectively correcting spin-contamination errors in molecular exchange coupling constant and spin crossover gap calculations.

Download Full-text

Hexaethyl-2,4-dicarba-nido-hexaborane(8), Deprotonation and Complexation Studied by NMR Spectroscopy and Density Functional Theory (DFT) Calculations

Zeitschrift für Naturforschung B ◽

10.1515/znb-2004-0609 ◽

2004 ◽

Vol 59 (6) ◽

pp. 685-691 ◽

Cited By ~ 8

Author(s):

Bernd Wrackmeyer ◽

Hans-Jörg Schanz

Keyword(s):

Density Functional Theory ◽

Nmr Spectroscopy ◽

Density Functional ◽

Chemical Shifts ◽

Coupling Constants ◽

Analogous Reaction ◽

Sandwich Complex ◽

Dft Methods ◽

Functional Theory ◽

Nmr Data

Deprotonation of hexaethyl-2,4-dicarba-nido-borane(8) 2 leads first to the hexaethyl-2,4-dicarbanido- borate(1−) 3, and further deprotonation, using BuLi/KOtBu, gives the hexaethyl-2,4-dicarbanido- hexaborate(2−) 4. The reaction of 3 with FeCl2 affords the commo-ferracarborane [Fe(Et6-2,4- C2B4H)2] 5, and the analogous reaction of 4 leads to the anionic sandwich complex [Fe(Et6-2,4- C2B4)2]2− 6 which can be protonated to give 5. The complex 5 contains two hydrido ligands, each bridging the iron and two boron atoms. Reactions were monitored and the products were characterised by 11B NMR spectroscopy in solution. The geometries of the carboranes, the borates (all unsubstituted and permethyl-substituted) and the iron complexes (all unsubstituted) were optimised by DFT methods [B3LYP/6-311+G(d,p) or B3LYP/6-31+G(d)], and the relevant NMR data [chemical shifts δ11B, δ13C, δ57Fe, and coupling constants 1J(13C,1H), 1J(11B,1H), 1J(57Fe,1H), 1J(57Fe,11B)] were calculated at the same level of theory.

Download Full-text