Positive and Negative Two-Dimensional Thermal Expansion via Relaxation of Node Distortions

Abstract

The ability to tune physical properties is attractive for the development of new materials for myriad applications. Understanding and controlling the structural dynamics in complicated network structures like coordination polymers (CPs) is particularly challenging. We report a series of two-dimensional CPs [Mn(salen)][M(CN)]· xHO (M = Pt (1), PtI (2), and MnN (3)) incorporating zigzag cyano-network layers that display composition-dependent anisotropic thermal expansion properties. Variable-temperature single-crystal X-ray structural analyses demonstrated that the thermal expansion behavior is caused by double structural distortions involving [Mn(salen)] units incorporated into the zigzag layers. Thermal relaxations produce structural transformations resulting in positive thermal expansion for 2·HO and negative thermal expansion for 3. In the case of 1·HO, the relaxation does not occur and zero thermal expansion results in the plane between 200 to 380 K. The present study proposes a new strategy based on structural distortions in coordination networks to control thermal responsivities of frameworks.

Node Distortion Modulation for Anisotropic Thermal Expansions of Two‐dimensional Coordination Polymers

“…We note that the contractions of layers by FeMnN and FePt also influenced the accommodation of lattice waters into crystals. While our previous works [8a] indicated that MnMnN incoporated two lattice waters immediately after the synthesis, the single‐crystal analysis for FeMnN indicated no lattice water. In the case of FePt , although it was indicated that intralayer hollows surrounded by [Fe(salen)] + units have low residual electron densities, a specific occupancy of lattice water molecules could not be determined unlike MnPt that incorporates one lattice water.…”

“… (a) Temperture dependences of lattice constant changes relative to the 150 K values for FeMnN and MnMnN [8a] (left), and for FePt and MnPt [8a] (right). (b) Thermal variation in the angles between tetracyanometallate units in the zigzag layers of FeMnN and MnMnN (left), and of FePt and MnPt (right).…”

“…These structural changes in the iron(III) systems were compared with those of their published manganese(III) analogues of type [Mn(salen)] 2 [M(CN) 4 ] (M=MnN ( MnMnN ) and Pt ( MnPt )) [8a] . Both for FeMnN and FePt , values of a and b axes are smaller while c axis values are larger than those of MnMnN and MnPt as shown in Table 1 (and please see also Figure S3 and Figure S4).…”

“…These cell parameter changes demonstrate contractions of the layers in the iron(III) systems compared with those of the respective manganese(III) analogues. The layers in FeMnN and FePt are also flatter than their Mn counterparts, which had a “zigzag” angle of 158.18(2)° ( MnMnN ) and 166.78(2)° ( MnPt ) (Figure 2(b)) [8a] . As a result, the layer distortions consisting of [FeO 2 N 4 ] octahedra with temperatures are less pronounced than that those of [MnO 2 N 4 ] (Figure 3, distortion angle A).…”

Crystal structure of poly[tetra(μ 2-cyanido-κ2 N:O)-bis(N,N-dimethylformamide-κO)-manganese(II)-platinum(II)], C10H14MnN6O2Pt

“…The crystal structures of the related heterometallic cyanido-bridged Mn-Pt-complexes [{Mn(salen)} 2 Pt(CN) 4 ] n (salen = N,N′-bis(salicylidene)ethylenediiminato) [5,6], [Mn(L)Pt(CN) 4 ] n (L = 2,13-dimethyl-3,12-diaza-6,9-dioxa-1(2,6)-pyridinacyclotridecaphane-2,12-diene) [7] and [Mn(phen) Pt(CN) 4 ] n (phen = 1,10-phenanthroline) [8] have been determined previously.…”