First Full Structural Characterization of Chloro Formamidinium Salts

Abstract

While the synthesis of chloro formamidinium chloride has been known for over one century, no solid‐state structure of a chlorine‐substituted formamidinium compound has been reported up to now. Herein, we describe syntheses, solid‐state structures, and vibrational properties of four chloro formamidinium compounds, namely [ClC(NH2)2]Cl (1), [ClC(NH2)2](AuCl4) (2), [ClC(NH2)2]2(PdCl4) (3), and [ClC(NH2)2]2(PtCl6) (4), as determined by single‐crystal X‐ray diffraction (SCXRD). 1 and 3 crystallize in the monoclinic space group P21/c, 2 in the orthorhombic space group Pbcn, whereas 4 adopts the triclinic space group P1. By using a combination of high‐resolution time‐of‐flight neutron powder diffraction, state‐of‐the‐art DFT calculations as well as IR spectroscopy, the prior SCXRD result was fully confirmed and augmented by determining the hydrogen‐bonded molecular networks. First‐principles electronic‐structure calculations corroborate the ionic nature of these salts by showing very flat, molecular‐like bands next to the Fermi level, in addition to indirect bandgaps. This study underlines the upmost importance of complementing diffraction data by ab initio calculations, as theory‐derived anisotropic displacement parameters served as fixed numerical entries.

Syntheses and Characterization of Diammine–Nickel/Cobalt(II)–Bisdicyanamide M(NH3)2[N(CN)2]2 with M = Ni and Co

“…Phonopy , and a custom-made MATLAB script , were then utilized to obtain anisotropic displacement parameters (ADPs) by using a frequency cutoff of 0.1 THz and 50 × 30 × 45 q -points. It has been previously shown that theoretically predicted ADPs can be successfully incorporated for structure refinements, such as refining the hydrogen positions whenever facing experimental issues . Furthermore, it was already demonstrated that theoretical ADPs of neutron quality correlate extremely well with the experimental counterparts, e.g., in the case of urea …”

Vibrational spectra of methylammonium iodide and formamidinium iodide in a wide temperature range

“…The wavenumbers of these bands are: The stretching vibrations of the NH2 groups in the FAI are located in the frequency region from 3400 to 3000 cm -1 . The origin of these bands can be additionally confirmed by the IR spectra obtained from the chloroformamidinium chloride [ClC(NH2)2]Cl [22]. In the low-temperature region, the number of bands is higher, but as the temperature increases, the bands shifts and they merge into one band (Fig.…”