[Mo₂(CN)₁₁]:^5- A Detailed Description of Ligand-Field Spectra and Magnetic Properties by First-Principles Calculations

Abstract

An ab initio multiconfigurational approach has been used to calculate the ligand-field spectrum and magnetic properties of the title cyano-bridged dinuclear molybdenum complex. The rather large magnetic coupling parameter J for a single cyano bridge, as derived experimentally for this complex by susceptibility measurements, is confirmed to a high degree of accuracy by our CASPT2 calculations. Its electronic structure is rationalized in terms of spin-spin coupling between the two constituent hexacyano-monomolybdate complexes. An in-depth analysis on the basis of Anderson's kinetic exchange theory provides a qualitative picture of the calculated CASSCF antiferromagnetic ground-state eigenvector in the Mo dimer. Dynamic electron correlations as incorporated into our first-principles calculations by means of the CASPT2 method are essential to obtain quantitative agreement between theory and experiment.

Spectroscopic Identification of the α-Fe/α-O Active Site in Fe-CHA Zeolite for the Low-Temperature Activation of the Methane C–H Bond

“…On the other hand, the highest energy d−d transition of the 1R NEAR model is calculated at only 10 592 cm −1 , which is outside of the error margin of 2000 cm −1 commonly accepted for CASPT2. 50,51 Moreover, the calculated Mossbauer parameters for the 1R OPPOSITE model closely match the experimental parameters (Table 2), although it is not possible to distinguish between the 1R OPPOSITE and 1R NEAR models solely based on the Mossbauer parameters.…”

“…Focusing on the two most prominent transitions in the electronic spectrum of α-Fe-CHA (5400 and 13 000 cm –1 ), close agreement with experiment is found for the CASPT2 excitation energies of the 1R OPPOSITE model (4065 and 13 478 cm –1 ). On the other hand, the highest energy d–d transition of the 1R NEAR model is calculated at only 10 592 cm –1 , which is outside of the error margin of 2000 cm –1 commonly accepted for CASPT2. , Moreover, the calculated Mössbauer parameters for the 1R OPPOSITE model closely match the experimental parameters (Table ), although it is not possible to distinguish between the 1R OPPOSITE and 1R NEAR models solely based on the Mössbauer parameters.…”

Analysis of the Magnetic Coupling in M3(dpa)4Cl2Systems (M = Ni, Pd, Cu, Ag) by Ab Initio Calculations

“…This method uses a CAS wave function as zeroth-order wave function and accounts for the remaining part of the electron correlation with second-order perturbation theory. Normally, CASPT2 gives rather satisfactory results provided that the CAS is large enough and properly chosen . This latter issue is important in the discussion of the results.…”

A Solid-State 95Mo NMR and Computational Investigation of Dodecahedral and Square Antiprismatic Octacyanomolybdate(IV) Anions: Is the Point-Charge Approximation an Accurate Probe of Local Symmetry?

“…Further Mo EFG and magnetic shielding tensor calculations were carried out on isolated molybdenum-containing anions and compounds possessing T d or O h symmetry: MoO 4 2- , MoS 4 2- , MoSe 4 2- , and Mo(CO) 6 , to establish the accuracy of the calculated molybdenum magnetic shielding (chemical shift) scale and to compare EFGs calculated using quantum chemistry computations with those determined using the PCA. Last, nonrelativistic ZORA DFT calculations of the Mo EFG tensors were carried out on a series of isolated, idealized anions possessing D 4 d symmetry, as well as various rotamers of Mo(CN) 8 , - including O h symmetry. The hypothetical Mo(CN) 8 4- anion possessing O h symmetry, i.e., a cube, was generated from that possessing D 4 d symmetry by rotating the upper portion of the square antiprism with respect to the bottom portion by 45°.…”

“…Interest in transition metal cyanides dates back to the early 1700s with the discovery of Prussian Blue . In recent years, interest in cyanometalates has been revived, in part, due to the utility of these anions as the building blocks of magnetic clusters and networks. − The classic textbook examples of eight-coordination transition metal cyanides are the molybdenum and tungsten octacyanide anions, , which have been known for nearly 100 years . These anions exist in both diamagnetic and paramagnetic forms, where the metal is in a formal oxidation state of +4 or +5, respectively. ,, Of particular interest is the ability of the (Mo, W) octacyanide anions to adopt different molecular arrangements which may be approximately described by the polyhedra illustrated in Figure .…”