Estimation of the Jahn-Teller stabilization energy in closed-shell transition-metal complexes

1995 ◽  
Vol 62 (4) ◽  
pp. 693-696 ◽  
Author(s):  
M. Grinberg ◽  
Cz. Koepke
Keyword(s):  
Transition Metal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Closed Shell ◽  
Stabilization Energy ◽  
Jahn Teller

scholarly journals A New Twist on an ‘Old’ Ligand: A [Mn16] Double Square Wheel and a [Mn10] Contorted Wheel

2020 ◽  
Author(s):  
Euan Brechin ◽  
Constantinos J. Milios ◽  
Thomais Tziotzi ◽  
Marco Coletta ◽  
Mark Gray ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Magnetic Susceptibility ◽  
Transition Metal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Direct Current ◽  
Coordination Compounds ◽  
Exchange Interactions ◽  
Ligand Design ◽  
Jahn Teller

Ligand design remains key to the synthesis of coordination compounds possessing specific topologies, nuclearities and symmetries that direct targeted physical properties. N,O-chelates based on ethanolamine have been particularly prolific in constructing a variety of paramagnetic 3d transition metal complexes with fascinating magnetic properties. Here, we show that combining three ethanolamine moieties within the same organic framework in the form of the ligand 1,3,5-tri(2-hydroxyethyl)-1,3,5-triazacyclohexane (LH3) leads to the formation of two highly unusual Mn wheels. Reaction of Mn(NO3)2·6H2O with LH3 in basic methanolic solutions leads to the formation of [MnIII 12MnII 4(µ3-O)6(µ-OH)4(µ3-OMe)2(µOMe)2(L)4(LH)2(H2O)10](NO3)6(OH)2 (1) and [MnIII 10(µ3-O)4(µ-OH)4(µ-OMe)4(L)4(H2O)4](NO3)2 (2); the only difference in the synthesis being the ratio of metal:ligand employed. The structure of the former describes two offset [MnIII 6MnII 2] square wheels, linked through a common centre, and the latter a single [MnIII 10] wheel twisted at its centre, such that the top half is orientated perpendicular to the bottom half. In both cases the L 3- /LH2- ligands dictate the orientation of the Jahn-Teller axes of the MnIII ions which lie perpendicular to the triazacyclohexane plane. Direct current magnetic susceptibility and magnetisation data reveal the presence of competing exchange interactions in 1 and strong antiferromagnetic interactions in 2. Given the simplicity of the reactions employed and the paucity of previous work, the formation of these two compounds suggests that LH3 will prove to be a profitable ligand for the synthesis of a multitude of novel 3d transition metal complexes

scholarly journals A New Twist on an ‘Old’ Ligand: A [Mn16] Double Square Wheel and a [Mn10] Contorted Wheel

2020 ◽  
Author(s):  
Euan Brechin ◽  
Constantinos J. Milios ◽  
Thomais Tziotzi ◽  
Marco Coletta ◽  
Mark Gray ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Magnetic Susceptibility ◽  
Transition Metal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Direct Current ◽  
Coordination Compounds ◽  
Exchange Interactions ◽  
Ligand Design ◽  
Jahn Teller

Ligand design remains key to the synthesis of coordination compounds possessing specific topologies, nuclearities and symmetries that direct targeted physical properties. N,O-chelates based on ethanolamine have been particularly prolific in constructing a variety of paramagnetic 3d transition metal complexes with fascinating magnetic properties. Here, we show that combining three ethanolamine moieties within the same organic framework in the form of the ligand 1,3,5-tri(2-hydroxyethyl)-1,3,5-triazacyclohexane (LH3) leads to the formation of two highly unusual Mn wheels. Reaction of Mn(NO3)2·6H2O with LH3 in basic methanolic solutions leads to the formation of [MnIII 12MnII 4(µ3-O)6(µ-OH)4(µ3-OMe)2(µOMe)2(L)4(LH)2(H2O)10](NO3)6(OH)2 (1) and [MnIII 10(µ3-O)4(µ-OH)4(µ-OMe)4(L)4(H2O)4](NO3)2 (2); the only difference in the synthesis being the ratio of metal:ligand employed. The structure of the former describes two offset [MnIII 6MnII 2] square wheels, linked through a common centre, and the latter a single [MnIII 10] wheel twisted at its centre, such that the top half is orientated perpendicular to the bottom half. In both cases the L 3- /LH2- ligands dictate the orientation of the Jahn-Teller axes of the MnIII ions which lie perpendicular to the triazacyclohexane plane. Direct current magnetic susceptibility and magnetisation data reveal the presence of competing exchange interactions in 1 and strong antiferromagnetic interactions in 2. Given the simplicity of the reactions employed and the paucity of previous work, the formation of these two compounds suggests that LH3 will prove to be a profitable ligand for the synthesis of a multitude of novel 3d transition metal complexes

scholarly journals Enumeration of de novo Inorganic Complexes for Chemical Discovery and Machine Learning

2019 ◽  
Author(s):  
Stefan Gugler ◽  
Jon Paul Janet ◽  
Heather Kulik
Keyword(s):  
Transition Metal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Density Functional ◽  
De Novo ◽  
Functional Materials ◽  
Closed Shell ◽  
Ligand Field ◽  
Structure Property ◽  
Computational Screening

<p>Despite being attractive targets for functional materials, the discovery of transition metal complexes with high-throughput computational screening is challenged by the amount of feasible coordination numbers, spin states, or oxidation states and the potentially large sizes of ligands. To overcome these limitations, we take inspiration from organic chemistry where full enumeration of neutral, closed shell molecules under the constraint of size has enriched discovery efforts. We design monodentate and bidentate ligands from scratch for the construction of mononuclear, octahedral transition metal complexes with up to 13 heavy atoms (i.e., metal, C, N, O, P, or S). From > 11,000 theoretical ligands, we develop a heuristic score for ranking a chemically feasible 2,500 ligand subset, only 71 of which were previously included in common organic molecule databases. We characterize the top 20% of scored ligands with density functional theory (DFT) in an octahedral homoleptic ligand database (OHLDB). The OHLDB contains i) the geometry optimized structures of 1,250 homoleptic octahedral complexes obtained from the enumerated pool of ligands and an open-shell transition metal (M(II)/M(III), M = Cr, Mn, Fe, or Co), and ii) the resulting high-spin/low-spin adiabatic electronic energies (<b>Δ</b><i>E</i><sub>H-L</sub>) obtained with hybrid DFT. Over the OHLDB, we observe structure–property (i.e., <b>Δ</b><i>E</i><sub>H-L</sub>) relationships different from those expected on the basis of ligand field arguments or from our prior data sets. Finally, we demonstrate how incorporating OHLDB data into artificial neural network (ANN) training improves ANN out-of-sample performance on much larger transition metal complexes.</p>

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