[show abstract][hide abstract] ABSTRACT: a b s t r a c t A complete theoretical characterization of a family of [Mo 6Àn W n Cl 8 F 6 ] 2À clusters where n = 0–6, was per-formed. The calculated geometrical parameters show a very good agreement with the previously reported experimental data. The assessed reactivity indexes indicate that the less reactive cluster would be [W 6 Cl 8 F 6 ] 2À which is in concordance with the fact that is the most energetically stable cluster. Rela-tivistic time-dependent density functional (TDDFT) calculations including spin–orbit interactions via the zeroth order regular approximation (ZORA) Hamiltonian and solvent effects were carried out for the clus-ter families. These calculations showed that the frontier molecular orbitals involved in the transitions are largely centered on the cubic [Mo 6Àn W n Cl 8 ] 4+ core and all the molecular orbitals involved in the calcu-lated transitions of each cluster are very much alike. More interestingly, the UV–Vis transitions are tuned and displaced to higher wavelength by the mixture of Mo and W atoms. Furthermore, our calculations and the electronic similarities with previously reported clusters, suggest that the clusters family [Mo 6À n W n Cl 8 F 6 ] 2À might show similar properties to those previously reported.
[show abstract][hide abstract] ABSTRACT: A family of octahedral molybdenum cluster complexes [Mo 6 Cl 8 (H 2 O) n (OH) 6Àn ] nÀ2 with n = 0–6 as a pH-sensors: A theoretical study a b s t r a c t Theoretical computations of a series of clusters [Mo 6 Cl 8 (H 2 O) n (OH) 6Àn ] nÀ2 are presented. UV–Vis absorp-tion spectra, the ground states (S 0) and the lowest excited states (S 1 and T 1) were examined. Energy dia-grams for luminescent decay were built in order to get insights about the emission processes of these systems. The fact that the systems show different emission energy profiles when the aqua and hydroxo coordinations are changed, indicates pH-dependence and supports the statement that these clusters are candidates to act as pH-sensors. Those properties are also shown by a reported family of luminescent [Re 6 S 8 (H 2 O) n (OH) 6Àn ] nÀ4 clusters, with the same structure of the systems studied here. Ó 2013 Elsevier B.V. All rights reserved.
Chemical Physics Letters 02/2013; · 2.15 Impact Factor
[show abstract][hide abstract] ABSTRACT: In this study we report about the aromaticity of the prototypical [(HtAc)3(μ2-H)6], [(HtTh)3(μ2-H)6]+, and [(HtPa)3(μ2-H)6] clusters via two magnetic criteria: nucleus-independent chemical shifts (NICS) and the magnetically induced current density. All-electron density functional theory calculations were carried out using the two-component zeroth-order regular approach and the four-component Dirac-Coulomb Hamiltonian, including scalar and spin-orbit relativistic effects. Four-component current density maps and the integration of induced ring-current susceptibilities clearly show that the clusters [(HtAc)3(μ2-H)6] and [(HtTh)3(μ2-H)6]+ are non-aromatic whereas [(HtPa)3(μ2-H)6] is anti-aromatic. However, for the thorium cluster we find a discrepancy between the current density plots and the classification through the NICS index. Our results also demonstrate the increasing influence of f orbitals, on bonding and magnetic properties, with increasing atomic number in these clusters. We think that the enhanced electron mobility in [(HtPa)3(μ2-H)6] is due the significant 5f character of its valence shell. Also the participation of f orbitals in bonding is the reason why the protactinium cluster has the shortest bond lengths of the three clusters. This study provides another example showing that the magnetically induced current density approach can give more reliable results than the NICS index.
The Journal of Chemical Physics 09/2011; 135(10):104506-104506-9. · 3.16 Impact Factor
[show abstract][hide abstract] ABSTRACT: Our calculations have shown that a series of the studied monosubstituted phenol deriva-tives containing substituents with different electronic effects on the ortho-, meta-and para-positions, show a direct relationship between the H-abstraction of the hydroxyl groups and the low values of nucleus-independent chemical shift ((NICS) activity, and these in turn are related to antioxidant activity, hence are in the lowest values of the enthalpy of dissociation, and this is demonstrated by the values of small NICS. All calculations of bond dissociation enthalpy (BDE) and the criterion of aromaticity ((NICS) were calculated using density functional theory (DFT) methods.
[show abstract][hide abstract] ABSTRACT: In our recent article (Chem. Phys. Lett. 2008, 467, 94-96), we reported the aromaticity via NICS calculations of the neutral Re(3)Cl(9) and Re(3)Br(9) clusters. Spin-orbit effects decrease their aromaticity due to the fact that the 5d(3/2) spinors are mostly occupied and are more contracted than the scalar 5d orbitals. Here, we report that the title anions are also aromatic but, oppositely, spin-orbit effects increase the clusters' aromaticity due to the fact that the 5d(5/2) spinors are now being populated and are more expanded than the scalar 5d orbital. All the clusters discussed here have larger induced diatropic ring currents than benzene.
The Journal of Physical Chemistry A 03/2009; 113(9):1671-3. · 2.77 Impact Factor
[show abstract][hide abstract] ABSTRACT: Here, we report density functional calculations of the electronic structure and nuclear independent chemical shift (NICS) values of the Re3Cl9 and Re3Br9 clusters including scalar and spin–orbit relativistic effects (ADF + ZORA + SO). Our calculations have shown that both the clusters exhibit aromaticity and that spin–orbit effects decreases aromaticity due to the fact that the 5d3/2 spinors are mostly occupied and are more contracted than the scalar 5d orbitals.
Chemical Physics Letters 12/2008; 467(s 1–3):94–96. · 2.15 Impact Factor