Clusters of solvated ferrous ion in water-ammonia mixture: Structures and noncovalent interactions

The behavior of metal ions is commonly studied in pure solvent although, in our daily life, these metals are involved in mixtures of solvents. In the present study, we investigated structures, relative stabilities and temperature dependance of solvated ferrous ion in water-ammonia mixture solvent at 0K and at various temperatures ranging from 25K to 400K. All the calculations are performed at the MN15 level of theory associated with the aug-cc-pVDZ basis set. For deep understanding of binding patterns in solvated ferrous ion in water-ammonia mixture solvent, noncovalent interactions are presented based on the QTAIM analysis using AIMAll. Our results prove that the ferrous ion is more stable when it is solvated by ammonia instead of water. In addition, hydrogen bonds are weakened by the presence of ammonia molecules. The temperature dependence of the different obtained geometries indicates that from s=6 (s is the sum of water and ammonia molecules around the ferrous ion), when the number of water molecules is almost equal to that of ammonia, the structures with coordination number 5 are dominant. However, the coordination number is six when there are a maximum water molecules (rich water solution) or maximum ammonia molecules (rich ammonia solution) around the ferrous ion (for s≥6). The QTAIM analysis shows that there are two coordination bondings and four hydrogen bondings. Furthermore, it is found that the Fe2+⋯N coordination bondings are stronger than the Fe2+⋯O confirming that the ferrous ion prefers to be solvated by ammonia instead of water.

Solvation energies of the ferrous ion in water and in ammonia at various temperatures

CONTEXT

The solvation of metal ions is crucial to understanding relevant properties in physics, chemistry, or biology. Therefore, we present solvation enthalpies and solvation free energies of the ferrous ion in water and ammonia. Our results agree well with the experimental reports for the hydration free energy and hydration enthalpy. We obtained [Formula: see text] kJ mol[Formula: see text] for the hydration free energy and [Formula: see text] kJ mol[Formula: see text] for the hydration enthalpy of ferrous ion in water at room temperature. At ambient temperature, we obtained [Formula: see text] kJ mol[Formula: see text] as the [Formula: see text] ammoniation free energy and [Formula: see text] kJ mol[Formula: see text] for the ammoniation enthalpy. In addition, the free energy of solvation is deeply affected when the temperature increases. This pattern can be attributed to the rise of entropy when the temperature rises. Besides, the temperature does not affect the ammoniation enthalpies and the hydration enthalpy of the [Formula: see text] ion.

METHOD

All the geometry optimizations are performed at the MP2 methods associated with the 6-31++g(d,p) basis set of Pople. solvated phase structures of [Formula: see text] ion in water or in ammonia are performed using the PCM model. The [Formula: see text] program suite was used to perform all the calculations. The program TEMPO was also used to evaluate the temperature sensitivity of the different obtained geometries.

Hydrogen bond networks of dimethylsulfoxide (DMSO) pentamer

Understanding of clusters of dimethylsulfoxide (DMSO) is important in several applications in Chemistry. Despite its importance, very few studies of DMSO clusters, (DMSO)_n, have been reported in comparison to systems such as water clusters or methanol clusters. In order to provide further understanding of DMSO clusters, we investigated the structures and non-covalent interactions of the (DMSO)_n, n=5. Therefore, the potential energy surface (PES) of the DMSO pentamer has been examined using classical molecular dynamics. The structures generated using classical molecular dynamics are further optimized at the PW6B95D3/aug-cc-pVDZ level of theory. To comprehend the non-covalent bondings in the DMSO pentamer, we carried out a quantum theory of atoms in molecule (QTAIM) analysis. In addition, the effects of temperature on the structural stability is investigated between 20 and 500K. It comes out that seven different kind of non-covalent bondings can be found in DMSO pentamers.

Conformational energies of microsolvated Na+ clusters with protic and aprotic solvents from GFNn-xTB methods

Performance of contemporary tight-binding semiempirical GFNn-xTB methods for the conformational energies of singly charged sodium clusters Na⁺ (S)_n (n = 4-8) with 3 protic and 8 aprotic solvents is examined against the reference RI-MP2/CBS method. The median Pearson correlation coefficients of ρ = 0.84 (GFN2-xTB) and ρ = 0.82 (GFN1-xTB) do not give the clear preference to any tested approach. GFN1-xTB method demonstrates more stable performance than its GFN2-xTB successor with the average mean absolute errors (MAEs)/mean signed errors (MSEs) of 1.2/0.2 and 2.3/1.6 kcal mol^-1 , respectively. Conformational energies produced by the computationally efficient DFT functional PBE and double-ζ basis set complemented with -D3(BJ) dispersion correction are suitable for the preliminary sampling (median ρ = 0.93), but should be used with a caution for the calculations of the average ensemble properties (MAE/MSE = 1.7/1.1 kcal mol^-1 ). Higher-ranking PBE0-D3(BJ) and ωB97M-V with triple-ζ basis sets yield significantly lower MAEs/MSEs of 0.55/0.20 and 0.51/0.23 kcal mol^-1 , respectively.

Structures, binding energies and non-covalent interactions of furan clusters

Understanding of the furan solvent is subjected to the knowledge of the structures of the furan clusters and interactions taking place therein. Although, furan clusters can be very important to determine the dynamics and the properties of the furan solvent, there has been only a few investigations reported on furan dimer. In this work, we have explored the potential energy surfaces (PESs) of the furan clusters using two incremental levels of theory. Structures have been initially generated using classical molecular dynamics followed by full optimization at the MP2/aug-cc-pVDZ level of theory. The results show that the most stable structure of the furan dimer has a stacking configuration while that of the trimer has a cyclic configuration. We have noted that the structures of the furan tetramer have no definite configurations. In addition, we have performed a quantum theory of atoms in molecule (QTAIM) analysis to identify all possible non-covalent interactions of the furan clusters. The results show that six different types of non-covalent interactions can be identified in furan clusters. We have noted that the CH⋯C and CH⋯O hydrogen bondings are the strongest non-covalent interactions while the H⋯H bonding interaction is found to be the weakest. Furthermore, we have assessed the performance of ten DFT functionals in calculating the binding energies of the furan clusters. The ten DFT functionals (M05, M05-2X, M06, M06-2X, M08HX, PBE0, ωB97XD, PW6B95D3, APFD and MN15) have been benchmarked to DLPNO-CCSD(T)/CBS. The functionals M05-2X and M06 are recommended for further affordable investigations of the furan clusters.

Structures and relative stability of hydrated ferrous ion clusters and temperature effects

Structures of solvated ferrous ion clusters have been investigated in the singlet and quintet spin states of the ferrous ion. Relative stabilities of isomers are also discussed at different temperatures.

Structures of the solvated copper(ii) ion in ammonia at various temperatures

We investigated theoretically the structures and relative stabilities of the solvated copper(ii) ion in ammonia, Cu²⁺(NH₃)_n, n = 1–10.

Global and local minima of protonated acetonitrile clusters

Potential energy surfaces of protonated acetonitrile clusters have been explored to locate global and local minima energy structures. The structures are stabilized by strong hydrogen bonds, anti-parallel dimers, dipole–dipole and CH⋯N interactions.