Metal-dependent ferro- versus antiferromagnetic interactions in molecular crystals of square planar {M(II) imino-nitroxide radical} complexes (M = Pt, Pd)
TANASE, Stefania
Inorganic Chemistry Laboratory-Faculty of Chemistry
Institut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
Inorganic Chemistry Laboratory-Faculty of Chemistry
Institut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
TUNA, Floriana
Institut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
Institute of Physical Chemistry
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Institut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
Institute of Physical Chemistry
TANASE, Stefania
Inorganic Chemistry Laboratory-Faculty of Chemistry
Institut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
Inorganic Chemistry Laboratory-Faculty of Chemistry
Institut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
TUNA, Floriana
Institut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
Institute of Physical Chemistry
< Reduce
Institut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
Institute of Physical Chemistry
Language
en
Article de revue
This item was published in
Inorganic Chemistry. 2003, vol. 42, n° 4, p. 1316-1321
American Chemical Society
English Abstract
The synthesis and structural, spectral, and magnetic characterizations of two new complexes of formula [Pt(IM2Py)Cl2] (A) and [Pd(IM2Py)Cl2] (B) are reported. IM2Py stands for the imino-nitroxide radical ligand ...Read more >
The synthesis and structural, spectral, and magnetic characterizations of two new complexes of formula [Pt(IM2Py)Cl2] (A) and [Pd(IM2Py)Cl2] (B) are reported. IM2Py stands for the imino-nitroxide radical ligand 2-(ortho-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl. Their crystal structures were solved at room temperature and at 120 K revealing structural phase transitions from pseudo-orthorhombic to monoclinic systems for the two compounds which remain isostructural in the whole temperature range explored. Structural parameters for A: T = 293 K [120 K], monoclinic (P21/n) [P21/c], a = 7.906(2) [7.989(3)] Å, b = 17.872(9) [10.168(4)] Å, c = 10.357(3) [17.623(6)] Å, = 90.732(13) [95.940(2)], Z = 4 [4]. Structural parameters for B: T = 293 K [120 K], monoclinic (P21/n) [P21/c], a = 7.900(3) [7.9730(2)] Å, b = 17.907(9) [10.1806(3)] Å, c = 10.299(3) [17.7171(4)] Å, = 90.524(14) [95.747(2)], Z = 4 [4]. In both complexes, the metal coordination is essentially planar. The average Pt-N, Pt-Cl and Pd-N, Pd-Cl bond lengths are 1.996(6) [1.88], 2.295(2) [2.248(8)] Å and 2.015(7) [2.029(8)], 2.287(3) [2.294(3)] Å, respectively. The solid state structure is characterized by a pairlike molecular packing stacked in columns parallel to the a axis; this dimer character is reinforced at low temperature. Despite their structural similarity, the investigation of the magnetic properties revealed that dominant ferromagnetic interactions govern the behavior of the Pt derivative A, whereas antiferromagnetic interactions take place for the Pd compound B. A rationalization for this rather intriguing difference is proposed in light of the spin population deduced from density functional theory calculations. The electronic absorption spectra of A and B present structured absorption bands in the visible which are attributed to MLCT transitions. Both compounds are nonluminescent at room temperature. However, a weak emission is detected for A in butyronitrile glasses at 77 K, indicating that the MLCT excited state is strongly quenched at low temperature.Read less <
Keywords
Luminescence
Ferromagnetic exchange
Antiferromagnetic exchange
Structural phase transition
Crystal structure
Molecular structure
Exchange interaction
Luminescence quenching
Origin
Hal imported