Formamidinium iodide: Crystal structure and phase transitions

At a temperature of 100K, CH5N2 +·I- (I), crystallizes in the monoclinic space group P21/c. The formamidinium cation adopts a planar symmetrical structure [the r.m.s. deviation is 0.002Å, and the C - N bond lengths are 1.301(7) and 1.309(8)Å]. The iodide anion does not lie within the cation plane, but deviates from it by 0.643(10)Å. The cation and anion of I form a tight ionic pair by a strong N-H⋯I hydrogen bond. In the crystal of I, the tight ionic pairs form hydrogen-bonded zigzag-like chains propagating toward [20-1] via strong N-H⋯I hydrogen bonds. The hydrogen-bonded chains are further packed in stacks along [100]. The thermal behaviour of I was studied by different physicochemical methods (thermogravimetry, differential scanning calorimetry and powder diffraction). Differential scanning calorimetry revealed three narrow endothermic peaks at 346, 387 and 525K, and one broad endothermic peak at ∼605K. The first and second peaks are related to solid-solid phase transitions, while the third and fourth peaks are attributed to the melting and decomposition of I. The enthalpies of the phase transitions at 346 and 387K are estimated as 2.60 and 2.75kJmol-1, respectively. The X-ray powder diffraction data collected at different temperatures indicate the existence of I as the monoclinic (100-346K), orthorhombic (346-387K) and cubic (387-525K) polymorphic modifications

Synthesis and crystal structure of a new hybrid methylammonium iodocuprate

The new hybrid organic-inorganic compound (MeNH3)Cu2I3 was synthesized using two independent techniques: mechanosynthesis and crystallization from acetonitrile. Its crystal structure was determined by single crystal X-ray diffraction. © 201

Formamidinium iodide: Crystal structure and phase transitions

At a temperature of 100K, CH5N2 +·I- (I), crystallizes in the monoclinic space group P21/c. The formamidinium cation adopts a planar symmetrical structure [the r.m.s. deviation is 0.002Å, and the C - N bond lengths are 1.301(7) and 1.309(8)Å]. The iodide anion does not lie within the cation plane, but deviates from it by 0.643(10)Å. The cation and anion of I form a tight ionic pair by a strong N-H⋯I hydrogen bond. In the crystal of I, the tight ionic pairs form hydrogen-bonded zigzag-like chains propagating toward [20-1] via strong N-H⋯I hydrogen bonds. The hydrogen-bonded chains are further packed in stacks along [100]. The thermal behaviour of I was studied by different physicochemical methods (thermogravimetry, differential scanning calorimetry and powder diffraction). Differential scanning calorimetry revealed three narrow endothermic peaks at 346, 387 and 525K, and one broad endothermic peak at ∼605K. The first and second peaks are related to solid-solid phase transitions, while the third and fourth peaks are attributed to the melting and decomposition of I. The enthalpies of the phase transitions at 346 and 387K are estimated as 2.60 and 2.75kJmol-1, respectively. The X-ray powder diffraction data collected at different temperatures indicate the existence of I as the monoclinic (100-346K), orthorhombic (346-387K) and cubic (387-525K) polymorphic modifications

Solution Processing of Methylammonium Lead Iodide Perovskite from γ-Butyrolactone: Crystallization Mediated by Solvation Equilibrium

The chemical origin of solvents typically used for preparation of hybrid lead halide perovskites - dimethyl sulfoxide (DMSO), dimethylformamide (DMF), and γ-butyrolactone (GBL) - strongly influences the process of perovskite crystallization because of the formation of intermediate adducts with different structures and morphology. The composition and crystal structures of the adducts depend on the coordination and binding ability of the solvents and the ratio of the precursors. New adducts of perovskite and GBL with either an unusual cluster structure, (MA)8(GBL)x[Pb18I44], or an adduct, (MA)2(GBL)2Pb3I8, similar to those observed for DMF and DMSO are described for the first time. Complex equilibriums between chemical species existing in perovskite solutions are revealed by Raman spectroscopy. As a result, new features of the perovskite crystallization through intermediate adduct phases are discussed, and effective perovskite deposition pathways are suggested. © 2018 American Chemical Society

Synthesis and crystal structure of a new hybrid methylammonium iodocuprate

The new hybrid organic-inorganic compound (MeNH3)Cu2I3 was synthesized using two independent techniques: mechanosynthesis and crystallization from acetonitrile. Its crystal structure was determined by single crystal X-ray diffraction. © 201

Self assembled nanoparticle patterns on carbon nanowall surfaces

We observed self-assembled quasiregular structures of diverse nanoparticles on a freestanding multilayer graphene-like material.</p

Solution Processing of Methylammonium Lead Iodide Perovskite from γ-Butyrolactone: Crystallization Mediated by Solvation Equilibrium

The chemical origin of solvents typically used for preparation of hybrid lead halide perovskites - dimethyl sulfoxide (DMSO), dimethylformamide (DMF), and γ-butyrolactone (GBL) - strongly influences the process of perovskite crystallization because of the formation of intermediate adducts with different structures and morphology. The composition and crystal structures of the adducts depend on the coordination and binding ability of the solvents and the ratio of the precursors. New adducts of perovskite and GBL with either an unusual cluster structure, (MA)8(GBL)x[Pb18I44], or an adduct, (MA)2(GBL)2Pb3I8, similar to those observed for DMF and DMSO are described for the first time. Complex equilibriums between chemical species existing in perovskite solutions are revealed by Raman spectroscopy. As a result, new features of the perovskite crystallization through intermediate adduct phases are discussed, and effective perovskite deposition pathways are suggested. © 2018 American Chemical Society

Formamidinium Haloplumbate Intermediates: The Missing Link in a Chain of Hybrid Perovskites Crystallization

A complete screening of compositions of crystallizing products of hybrid perovskites in the most popular dimethylformamide (DMF)/dimethyl sulfoxide (DMSO) solvents is performed for various cations (FA+/MA+) and anions (I-/Br-). We found four new solvate phases of formamidinium hybrid perovskites, (FA)2Pb3I8·4DMF, FAPbI3·2DMF, (FA)5Pb2I9·0.5DMSO, and even the bromide solvate (FA)2PbBr4·DMSO. These compounds are observed for the first time, and their refined crystal structures showed large cells of unique types dependent on solvent and perovskite compositions. We also monitored crystallization pathways of multicompositional thin films and identified phases that are able to crystallize from mixed cation and anion solutions. Based on the obtained data, we performed a deep analysis of the structural peculiarities of all the solvate phases observed in the screened compositional space and discussed how the solution composition would predetermine the early stages of crystallization of target perovskite films. Copyright © 2020 American Chemical Society

FA₂PbBr₄: Synthesis, Structure, and Unusual Optical Properties of Two Polymorphs of Formamidinium-Based Layered (110) Hybrid Perovskite

Small cations such as guanidinium and cesium can act as templating cations to form low-dimensional perovskite-like phases (two-dimensional (2D), one-dimensional (1D), zero-dimensional (0D)) in the case of an excess of organic halides. However, such phases with the widely used formamidinium (FA+) cations have not been reported so far. In this study, we discovered two novel low-dimensional phases with FA2PbBr4 composition and investigated the prerequisites of their formation on the crystallization of FABr-excessive solutions of FAPbBr3. We found that both phases have the structure of (110) layered perovskite but are represented by two different polymorphs with "eclipsed"and "staggered"arrangement of adjacent layers. It was shown that FA2PbBr4 phases usually exist in a labile equilibrium with the FAPbBr3 three-dimensional (3D) perovskite and can form composites with it. The optical properties of both polymorphs were comprehensively studied by means of absorption spectroscopy, diffuse reflection spectroscopy, and photoluminescence spectroscopy. Density functional theory (DFT) calculations were applied to investigate the band structure of the FA2PbBr4 and to corroborate the conclusions on their optoelectronic properties. As a result, we found that FA2PbBr4 phases irradiated by UV can exhibit effective green photoluminescence due to the transfer of excitation energy to defective states or 3D perovskite inclusions