Synthesis and thermal decomposition of Cr–urea complex

Bai, Mingmin; Zhao, S.; Asuha, S.

doi:10.1007/s10973-013-3260-7

Cited by 6 publications

(2 citation statements)

References 19 publications

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“…With its propensity to form dense hydrogen bond networks, urea represents a particularly promising ligand for metal–organic PCMs, but rapid decomposition within melts effectively rules out its usefulness for reversible thermal energy storage. , To target high hydrogen bond densities without decomposition or undesirable reactivity in the liquid phase, we thus began by exploring coordination complexes of N -methylurea (MeUr), where the addition of a methyl group trades one hydrogen bond donor for substantially improved thermal stability. When combined with divalent metal halide or nitrate salts, MeUr forms a series of octahedral complexes [M(MeUr) 6 ]X 2 (M = Mg, Ca, Mn, Co, Ni, Cu, Zn; X = Cl or NO 3 ). , Within these compounds, octahedral metal centers direct the formation of intramolecular hydrogen bonds between the metal-bound carbonyl O atoms and the N–H groups on adjacent MeUr ligands and of extended networks of intermolecular hydrogen bonds between MeUr ligands and uncoordinated anions (Figure a and Figure S6, Tables S4–S7).…”

Section: Results and Discussionmentioning

confidence: 99%

Metal–Organic Phase-Change Materials for Thermal Energy Storage

et al. 2020

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The development of materials that reversibly store high densities of thermal energy is critical to the more efficient and sustainable utilization of energy. Herein, we investigate metal− organic compounds as a new class of solid−liquid phase-change materials (PCMs) for thermal energy storage. Specifically, we show that isostructural series of divalent metal amide complexes featuring extended hydrogen bond networks can undergo tunable, high-enthalpy melting transitions over a wide temperature range. Moreover, these coordination compounds provide a powerful platform to explore the specific factors that contribute to the energy density and entropy of metal−organic PCMs. Through a systematic analysis of the structural and thermochemical properties of these compounds, we investigated the influence of coordination bonds, hydrogen-bond networks, neutral organic ligands, and outer-sphere anions on their phase-change thermodynamics. In particular, we identify the importance of high densities of coordination bonds and hydrogen bonds to achieving a high PCM energy density, and we show how metal-dependent changes to the local coordination environment during melting impact the entropy and enthalpy of metal−organic PCMs. These results highlight the potential of manipulating order− disorder phase transitions in metal−organic materials for thermal energy storage.

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Section: Results and Discussionmentioning

confidence: 99%

Metal–Organic Phase-Change Materials for Thermal Energy Storage

et al. 2020

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“…In this typical reaction, a direct solid-state reaction between Cr(NO 3 ) 3 Á9H 2 O and NH 2 CONH 2 in a weight ratio of 1 : 6 led to the formation of the Cr-urea complex [Cr(NH 2 CONH 2 ) 6 ](NO 3 ) 3 . 38 The obtained complex was heated at 350 1C in an alumina crucible with a loosely roofed lid. According to work published by House and co-workers, it is expected that the Cr-urea complex transmutes into an intermediate complex of [Cr(NCO)(NH 3 ) 5 ](NO 3 ) 2 by thermal decomposition at 140 1C where the ligand (NCO À ) forms Cr-N and Cr-O type bonds.…”

Section: Formation Mechanism Of Crn Nanoparticlesmentioning

confidence: 88%