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Title: Temperature dependence of the spin state and geometry in tricobalt paddlewheel complexes with halide axial ligands

Abstract

Trinuclear cobalt paddlewheel complexes, [Co3(dpa)4X2] (dpa = the anion of 2,2'-dipyridylamine, X = Cl–, Br–, –NCS–, –CN–, (NC)2N–), are known to demonstrate a thermally-induced spin-crossover (SCO). Despite a wealth of structural and magnetic information about such complexes, the role of the axial ligand on the characteristic SCO temperature (T1/2) remains ambiguous. The situation is complicated by the observation that the solid state geometry of the complexes, symmetric or unsymmetric, with respect to the central cobalt ion, also appears to influence the SCO behavior. In order to seek trends in the relationship between the nature of the axial ligand, geometry and magnetic properties, we have prepared the first examples of tricobalt paddlewheel complexes with axial fluorido and iodido ligands, as well as two new chlorido and bromido solvates. Their SCO properties are discussed in the context of an examination of previously reported chlorido and bromido adducts. The main conclusions are: (1) T1/2 values follow the trend I– < Br– ≈ Cl– < F–; (2) while the molecular geometry is predominantly guided by crystal packing for the Cl–, Br– and I– derivatives, the presence of an axial fluoride may favor a more symmetric core; (3) the magnetic characterization of a second examplemore » of an unsymmetric complex supports the observation that they display dramatically lower T1/2 values than their symmetric analogues; and (4) SCO in crystallographically symmetric compounds apparently occurs without loss of molecular or crystallographic symmetry, while a gradual geometric transformation linking the temperature dependence of quasi-symmetric to unsymmetric in crystallographically unconstrained compounds was found.« less

Authors:
 [1]; ORCiD logo [2]; ORCiD logo [1];  [1]; ORCiD logo [3]; ORCiD logo [4]; ORCiD logo [1]
  1. Centre National de la Recherche Scientifique (CNRS), Pessac (France). Centre de Recherche en Physique des Plasma (CRPP); Univ. of Bordeaux (France)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. Univ. of Zaragoza (Spain)
  4. Univ. of Oxford (United Kingdom)
Publication Date:
Research Org.:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
OSTI Identifier:
1560410
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
Dalton Transactions
Additional Journal Information:
Journal Volume: 47; Journal Issue: 46; Journal ID: ISSN 1477-9226
Publisher:
Royal Society of Chemistry
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Srinivasan, Anandi, Wang, Xiaoping, Clérac, Rodolphe, Rouzières, Mathieu, Falvello, Larry R., McGrady, John E., and Hillard, Elizabeth A. Temperature dependence of the spin state and geometry in tricobalt paddlewheel complexes with halide axial ligands. United States: N. p., 2018. Web. doi:10.1039/C8DT03833C.
Srinivasan, Anandi, Wang, Xiaoping, Clérac, Rodolphe, Rouzières, Mathieu, Falvello, Larry R., McGrady, John E., & Hillard, Elizabeth A. Temperature dependence of the spin state and geometry in tricobalt paddlewheel complexes with halide axial ligands. United States. https://doi.org/10.1039/C8DT03833C
Srinivasan, Anandi, Wang, Xiaoping, Clérac, Rodolphe, Rouzières, Mathieu, Falvello, Larry R., McGrady, John E., and Hillard, Elizabeth A. Thu . "Temperature dependence of the spin state and geometry in tricobalt paddlewheel complexes with halide axial ligands". United States. https://doi.org/10.1039/C8DT03833C. https://www.osti.gov/servlets/purl/1560410.
@article{osti_1560410,
title = {Temperature dependence of the spin state and geometry in tricobalt paddlewheel complexes with halide axial ligands},
author = {Srinivasan, Anandi and Wang, Xiaoping and Clérac, Rodolphe and Rouzières, Mathieu and Falvello, Larry R. and McGrady, John E. and Hillard, Elizabeth A.},
abstractNote = {Trinuclear cobalt paddlewheel complexes, [Co3(dpa)4X2] (dpa = the anion of 2,2'-dipyridylamine, X = Cl–, Br–, –NCS–, –CN–, (NC)2N–), are known to demonstrate a thermally-induced spin-crossover (SCO). Despite a wealth of structural and magnetic information about such complexes, the role of the axial ligand on the characteristic SCO temperature (T1/2) remains ambiguous. The situation is complicated by the observation that the solid state geometry of the complexes, symmetric or unsymmetric, with respect to the central cobalt ion, also appears to influence the SCO behavior. In order to seek trends in the relationship between the nature of the axial ligand, geometry and magnetic properties, we have prepared the first examples of tricobalt paddlewheel complexes with axial fluorido and iodido ligands, as well as two new chlorido and bromido solvates. Their SCO properties are discussed in the context of an examination of previously reported chlorido and bromido adducts. The main conclusions are: (1) T1/2 values follow the trend I– < Br– ≈ Cl– < F–; (2) while the molecular geometry is predominantly guided by crystal packing for the Cl–, Br– and I– derivatives, the presence of an axial fluoride may favor a more symmetric core; (3) the magnetic characterization of a second example of an unsymmetric complex supports the observation that they display dramatically lower T1/2 values than their symmetric analogues; and (4) SCO in crystallographically symmetric compounds apparently occurs without loss of molecular or crystallographic symmetry, while a gradual geometric transformation linking the temperature dependence of quasi-symmetric to unsymmetric in crystallographically unconstrained compounds was found.},
doi = {10.1039/C8DT03833C},
journal = {Dalton Transactions},
number = 46,
volume = 47,
place = {United States},
year = {Thu Nov 15 00:00:00 EST 2018},
month = {Thu Nov 15 00:00:00 EST 2018}
}

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