Two Shared Icosahedral Metallacarboranes through Iron: A Joint Experimental and Theoretical Refinement of Mössbauer Spectrum in [Fe(1,2-C2B9H11)2]Cs

SUBJECTS:Anions,Conformation,Energy,Molecular structure,Quantum mechanicsMössbauer and X-ray photoelectron spectroscopies (XPS) are complemented with high-level quantum-chemical computations in the study of the geometric and electronic structure of the paramagnetic salt of the metallacarborane sandwich complex [Fe(1,2-CBH)]Cs = FeSanCs. Experimental Fe isomer shifts and quadrupole splitting parameters are compared with the theoretical prediction, with good agreement. The appearance of two sets of Cs(3d) doublets in the XPS spectrum, separated by 2 eV, indicates that Cs has two different chemical environments due to ease of the Cs cation moving around the sandwich complex with low-energy barriers, as confirmed by quantum-chemical computations. Several minimum-energy geometries of the FeSanCs structure with the corresponding energies and Mössbauer parameters are discussed, in particular the atomic charges and spin population and the surroundings of the Fe atom in the complex. The Mössbauer spectra were taken at different temperatures showing the presence of a low-spin Fe atom with S = 1/2 and thus confirming a paramagnetic Fe species.We are grateful to Prof. Ibon Alkorta (IQM-CSIC) for providing the MEP of trans-FeSan anion conformer. J.F.M. and J.Z.D.-P. acknowledge financial support from grant RTI2018-095303-B-C51 funded by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe” and from grant S2018-NMT-4321 funded by the Comunidad de Madrid and by “ERDF A way of making Europe”. M.F., J.E., and J.M.O.-E. are grateful to Ministerio de Ciencia, Innovacióny Universidades, for financial support with grant number PID2021-125207NB-C32. O.B.O. and D.R.A. acknowledge the financial support from the Universidad de Buenos Aires (grant no. 20020190100214BA), the Consejo Nacional de Investigaciones Científicas y Técnicas (grant nos PIP11220200100467CO, PIP 11220130100377CO, and PIP11220130100311CO), and the Agencia Nacional de Promoción Científica y Tecnológica, Argentina (grant no. PICT-201-0381).Peer reviewe

Topology of molecular electron density and electrostatic potential with DAMQT

A new version of the DAMQT package incorporating topological analysis of the molecular electron density and electrostatic potential is reported. Evaluation of electron density, electrostatic potential and their first and second derivatives within DAM partition-expansion is discussed, and the pertaining equations are reported. An efficient algorithm for the search of critical points, gradient paths, atomic basins and Hessian analysis is implemented using these equations. 3D viewer built in DAMQT incorporates new facilities for visualization of these properties, as well as for distance and angle measurements. Full control of projection mode is also added to the viewer in DAMQT. Some examples are provided showing the excellent performance for large molecular systems

DAMQT 3: Advanced suite for the analysis of molecular density and related properties in large systems

A new version of the DAMQT package specially developed for large systems is reported. The graphical part has been entirely redesigned, using new OpenGL libraries (versions 3.3 or higher) for 3D display. Several 2D plotters and 3D viewers can be launched now in the same session and more than one molecule can be loaded in the same 3D window. Algorithms have been rescaled and modified to work with densities coming from ZDO computations in very big molecular systems (up to thousands of atoms) at a very moderate cost. New functionalities have been added including computation of molecular electrostatic potential over a molecular surface determined as a user-defined density isosurface. The method of Electrostatics for Intermolecular Complexation has been added to the package to serve as an auxiliary tool for cluster geometry optimization. Examples are provided which prove the good performance of the algorithms. Program summary: Program Title: DAMQT_3 CPC Library link to program files: https://doi.org/10.17632/2rxvgbsnhx.2 Licensing provisions: GPLv3 Programming language: Fortran90, C++ and Python Supplementary material: Quick-start guide and User's manual in PDF format included in the package. User's manual is also accessible from the GUI. External routines/libraries: Qt (5.10 or higher), OpenGL (3.3 or higher), ffmpeg (3.4 or higher), OpenBabel (2.3 or higher, optional) Nature of problem: Analysis and visualization of the molecular electron density, electrostatic potential, critical points, gradient paths, atomic basins, electric field and Hellmann-Feynman forces on nuclei, clusters optimization with EPIC. Solution method: Molecular electron density is partitioned into (pseudo)atomic fragments by means of the method of Deformed Atoms in Molecules [1]. Electron densities of the fragments are expanded as a series of spherical harmonics times radial factors. The partition is used for defining molecular density deformations and for the fast calculation of several properties associated with density, including electrostatic potential, electric field and Hellmann-Feynman forces over nuclei. Exploration of density and potential topology is facilitated, and the computation of electrostatic potential over an isodensity surface is implemented. Cluster optimization facility with EPIC is also implemented. Additional comments including restrictions and unusual features: Density matrix must come from an LCAO calculation (any computational level) with spherical (not Cartesian) Slater or Gaussian functions. The program contains an OPEN statement to binary files (stream) in several files. This statement does not have a standard syntax in Fortran 90. Two possibilities are considered in conditional compilation: Intel's ifort and Fortran2003 standard. This latter is applied to compilers other than ifort (gfortran uses this one, for instance). References: [1] J. Fernández Rico, R. López, I. Ema, G. Ramírez, J. Mol. Struct., Theochem 727 (2005) 11