Low temperature phase transition induced biaxial negative thermal expansion of 2,4-dinitroanisole

Abstract

The crystal structure of 2,4-dinitroanisole (24DNAN) is known to have two polymorphic structures (Z′ = 2 and Z′ = 1, hereafter referred to as α-form and β-form, respectively) and the oxygen atoms of the nitro group(s) of both polymorphs have been found to be disordered over two positions at 298 K. In the thermal behaviour studies of 24DNAN, the β-form showed a phase transition at 264.5 K on cooling. To investigate this phase transition variable-temperature single-crystal X-ray diffraction measurements were carried out.The β angle for the β-form dramatically changed from 90.190°(298 K) to 96.716°(100 K). The length of the b axis shows negative thermal expansion, 13.741(5) to 13.810(5) Å (with a change in temperature from 298 K to 100 K). The thermal expansion coefficients along the principal axes X1, X2, and X3 are −31IJ6), −15IJ7) and 262(20) MK −1 (261-100 K), respectively. 24DNAN showed an unusual biaxial NTE induced by a low temperature phase transition.

A survey of thermal expansion coefficients for organic molecular crystals in the Cambridge Structural Database

“…Structure-property relationships in crystalline materials are of fundamental importance for a huge range of research and practical applications, and the control and design of such properties is at the heart of crystal engineering. For molecular materials, thermal expansion has received some attention in the literature, for example where structures show unusually large or exceptionally anisotropic expansion (Das et al, 2010;Takahashi & Tamura, 2015;Alimi et al, 2018;van der Lee et al, 2018;Liu et al, 2019). There have also been some efforts in the crystal engineering literature to link thermal expansion to intermolecular interactions and specific structural features Bhattacharya & Saha, 2014;Saraswatula et al, 2015;Hutchins et al, 2016;Rather & Saha, 2018;Hutchins et al, 2018a;Negi et al, 2018).…”

Guest-dependent negative thermal expansion in a lanthanide-based metal–organic framework

“…15 In many instances, the NTE effect becomes more evident as a material approaches a phase transition. 16 A typical example of such a behaviour is PbTiO3 perovskite, which exhibits increasingly stronger NTE effect near its ferroelectricparaelectric phase transition. 17 NTE observed exclusively below the magnetic ordering temperature in CuO and MnF2 18 is reminiscent of the Invar effect, i.e.…”

Single-crystal-to-single-crystal transformations triggered by dehydration in polyoxometalate-based compounds

“…The SCSC transformation phenomenon has been described in recent years for several different types of both purely organic (Centore et al, 2015;Takahashi & Tamura, 2015;Hagihara et al, 2015;Mouchaham et al, 2015;Khorasani et al, 2015) and inorganic systems (Zakharov et al, 2015;Avdeeva et al, 2015), as well as for a vast number of coordination compounds based on the combination of metal-ion centres and organic ligands that includes metal-organic frameworks (MOFs) of covalent or supramolecular nature (Neogi et al, 2014;Ren et al, 2015;Manna et al, 2015;Lee et al, 2015) and porous coordination polymers (Li et al, 2015;Coronado et al, 2012;Tahier & Oliver, 2015;Aromí et al, 2016) beyond simple Comparison between hybrid layers in the crystallographic ac plane and solvent-accessible spaces viewed along the crystallographic c axis for coordination complexes. In contrast, literature reports on SCSC transitions involving compounds that incorporate polyoxometalate (POM) clusters are comparatively much less common (Reinoso et al, 2016), despite the fact that solid-state transformations have been known for decades in POM chemistry, as exemplified by the thermally-triggered isomerization of the trilacunary [PW 9 O 34 ] 9À Keggin-type cluster from the A-form into the B-derivative (Finke et al, 1987).…”