NDLI: Density functional studies on dinuclear $\{Ni^{II}Gd^{III}\}$ and trinuclear $\{Ni^{II}Gd^{III}Ni^{II}\}$ complexes: magnetic exchange and magneto-structural maps

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Tibrewal, Neeraj Kumar Singh, Saurabh Kumar Rajaraman, Gopalan
Description	Author Affiliation: Singh SK ( Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.)
Abstract	Theoretical calculations using density functional methods have been performed on two dinuclear $\{Ni^{II}–Gd^{III}\}$ and two trinuclear $\{Ni^{II}–Gd^{III}–Ni^{II}\}$ complexes having two and three μ-OR (R = alkyl or aromatic groups) bridging groups. The different magnetic behaviour, having moderately strong ferromagnetic coupling for complexes having two μ-OR groups and weak ferromagnetic coupling for complexes having three μ-OR groups, observed experimentally is very well reproduced by the calculations. Additionally, computation of overlap integrals MO and NBO analysis reveals a clear increase in antiferromagnetic contribution to the net exchange for three μ-OR bridged {Ni–Gd} dimers and also provides several important clues regarding the mechanism of magnetic coupling. Besides, MO and NBO analysis discloses the role of the empty 5d orbitals of the $Gd^{III}$ ion on the mechanism of magnetic coupling. Magneto-structural correlations for Ni–O–Gd bond angles, Ni–O and Gd–O bond distances, and the Ni–O–Gd–O dihedral angle have been developed and compared with the published experimental {Ni–Gd} structures and their J values indicate that the Ni–O–Gd bond angles play a prominent role in these types of complexes. The computation has then been extended to two trinuclear $\{Ni^{II}–Gd^{III}–Ni^{II}\}$ complexes and here both the {Ni–Gd} and the {Ni–Ni} interactions have been computed. Our calculations reveal that, for both structures studied, the two {NiGd} interactions are ferromagnetic and are similar in strength. The {Ni–Ni} interaction is antiferromagnetic in nature and our study reveals that its inclusion in fitting the magnetic data is necessary to obtain a reliable set of spin Hamiltonian parameters. Extensive magneto-structural correlations have been developed for the trinuclear complexes and the observed J trend for the trinuclear complex is similar to that of the dinuclear {Ni–Gd} complex. In addition to the structural parameters discussed above, for trinuclear complexes the twist angle between the two Ni–O–Gd planes is also an important parameter which influences the J values.
ISSN	14779226
Issue Number	41
Journal	Dalton Trans.
Volume Number	40
e-ISSN	13645447
Language	English
Publisher	Royal Society of Chemistry
Publisher Date	2011-11-07
Publisher Place	Great Britain (UK)
Access Restriction	Subscribed
Subject Keyword	Chemistry
Content Type	Text
Resource Type	Article
Subject	Inorganic Chemistry

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