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

Journal Article · · Dalton Transactions
DOI:https://doi.org/10.1039/C8DT03833C· OSTI ID:1560410
 [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)
+ Show Author Affiliations

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.

Research Organization:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
Grant/Contract Number:
AC05-00OR22725
OSTI ID:
1560410
Journal Information:
Dalton Transactions, Vol. 47, Issue 46; ISSN 1477-9226
Publisher:
Royal Society of ChemistryCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 2 works
Citation information provided by
Web of Science

References (17)

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Linked Research (19)

Figures / Tables (12)

Chart 1(p. 2)figure Chart 1
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Table 1(p. 4)table Table 1
Table 2(p. 4)table Table 2
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Fig. 3(p. 6)figure Fig. 3
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Fig. 4(p. 7)figure Fig. 4
Table 6(p. 7)table Table 6
Fig. 5(p. 8)figure Fig. 5

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