Homo- and Heterosolvent Modifications of Hofmann-Type Flexible Two-Dimensional Layers for Colossal Interlayer Thermal Expansions

Abstract

Two-dimensional Hofmann-type coordination polymers of type Mn­(H2O)2[Pd­(CN)4]·xH2O (1· x H 2 O; x = 0, 1, and 4), Mn­(H2O)­(MeOH)­[Pd­(CN)4]·2MeOH (2·2MeOH), and Mn­(MeOH)2[Pd­(CN)4]·MeOH (3·MeOH) have been synthesized. The homosolvent-bound 1·4H 2 O, 1·H 2 O, and 3·MeOH polymers consist of undulating layer structures, whereas the structure of heterosolvent-bound 2·2MeOH consists of “Janus-like” flat layers in which water-bound and MeOH-bound-sides are present. 1·4H 2 O and 1·H 2 O exhibited anisotropic two-dimensional thermal expansions involving structural transformations of the undulating layers; one layer axis expands while the other contracts. 2·2MeOH exhibits anisotropic thermal expansion in which the flat layers shift sideways as the temperature is increased, with colossal interlayer expansion occurring (αc = +200 MK–1 over 140–180 K, αc = +165 MK–1 over 200–280 K). 3·MeOH also showed colossal interlayer expansion (αc = +216 MK–1) together with expansion of the undulating layers.

Responsive Four‐Coordinate Iron(II) Nodes in FePd(CN)4

“…We used scanning transmission electron microscopy (STEM) [9] to comprehend the overall crystal structure of the fully-dehydrated FePd-(CN) 4 CP.I na ni nterpenetrated 3D PtS-type FePd(CN) 4 network, the coordination geometry of Fe II is not only anomalously distorted but can also act as af lexible node, inducing anisotropic thermal expansion (TE) behaviors, including uniaxial positive TE and large NTE along the other axes. 2 •4 H 2 Odemonstrated that its structure is similar to that of previously reported compounds with ac yanide-bridged 2D layer, [10] with two water molecules coordinated to the axial sites of the Fe II ions and the other four in the lattice (Figure 1a;S upporting Information, Table S1). Theb ond lengths of FeÀNa nd FeÀOa re 2.142(3) and 2.164(3) ,r espectively.T he infrared (IR) spectrum of 1(H 2 O) 2 •4 H 2 Odisplays the characteristic stretching mode of the bridging CN À ligands at 2169 cm À1 ,along with peaks corresponding to water molecules (Supporting Information, Figure S1).…”

“…Thermogravimetry-differential thermal analysis (TG-DTA) showed that the weight loss occurred in two steps:through the removal of four lattice water molecules at 340 Kand two bound water molecules at 390 K(Supporting Information, Figure S2), while no weight loss was observed for the fully-dehydrated form, up to 600 K. ( Figure 1b,c). [10] Compound 1 was obtained by the thermal treatment of 1(H 2 O) 2 •4 H 2 Oa t5 53 Kf or 30 min (Supporting Information, Figure S3). TheI Rs pectrum of 1 shows the characteristic stretching mode of CN À ligands at 2181 cm À1 (Supporting Information, Figure S1).…”

Responsive Four‐Coordinate Iron(II) Nodes in FePd(CN)4

“… Crystal structures of a) 1 (H 2 O) 2 ⋅4 H 2 O and b) Mn(H 2 O) 2 Pd(CN) 4 ⋅H 2 O for comparison . c) PXRD results for 1 (H 2 O) 2 ⋅4 H 2 O, 1 (H 2 O) 2 ⋅H 2 O, and 1 .…”

New family of Hofmann-like coordination polymers constructed with imidazole ligands and associated with spin crossover and anisotropic thermal expansions

“…But NTE behaviour has been investigated much less extensively for Hofmann-like 2D compounds with organic ligands. 9,[11][12][13][14] Research on cyano-bridged CPs without any other organic ligands indicated the mechanism of the fence effect to be due to the transverse CN vibrational modes. 32 Consequently, in that previous work, a large compound displaying anisotropic TE shows highly bent, zig-zag cyano-bridged layer structures.…”

“…Recently, negative thermal expansion (NTE) behavior in Hofmann-like 2D layer has been investigated. 9,10 However, there are few reports of a coexistence of SCO with anisotropic TE. An ability to consider a combination of lattice expansion (NTE) and rapid lattice contraction (SCO), i.e.…”