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Joint Experimental and Computational Investigation of the Flexibility of a Diacetylene‐Based Mixed‐Linker MOF: Revealing the Existence of Two Low‐Temperature Phase Transitions and the Presence of Colossal Positive and Giant Negative Thermal Expansions
Author(s) -
Duarte Rodrigues Alysson,
Fahsi Karim,
Dumail Xavier,
Masquelez Nathalie,
van der Lee Arie,
MalletLadeira Sonia,
Sibille Romain,
Filhol JeanSébastien,
Dutremez Sylvain G.
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201703711
Subject(s) - diacetylene , phase transition , materials science , crystallography , phase (matter) , diffraction , single crystal , isophthalic acid , chemistry , thermodynamics , polymer , physics , polymerization , organic chemistry , optics , composite material , polyester , terephthalic acid
Abstract Solvothermal reaction in N , N ‐dimethylformamide (DMF) between 1,6‐bis(1‐imidazolyl)‐2,4‐hexadiyne monohydrate ( L1⋅ H 2 O), isophthalic acid ( H 2 L2 ), and Zn(NO 3 ) 2 ⋅ 6 H 2 O gives the diacetylene‐based mixed‐ligand coordination polymer {[Zn( L1 )( L2 )](DMF) 2 } n ( UMON‐44 ) in 38 % yield. Combination of DSC with variable‐temperature single‐crystal X‐ray diffraction revealed the occurrence of two phase transitions spanning the ranges 129–144 K and 158–188 K. Furthermore, the three structurally similar phases of UMON‐44 show giant negative and/or colossal positive thermal expansions. These unusual phenomena exist without any change in the contents of the unit cell. DFT calculations using the PBE+D3 dispersion scheme were able to distinguish between these polymorphs by accurately reproducing their salient structural features, although corrections in the size of the unit cell turned out to be necessary for the high‐temperature phase to account for its large thermal expansion. In addition, the infrared spectra (vibration frequencies and peak intensities) of these theoretical models were calculated, allowing for univocal identification of the corresponding polymorphs. Last, the limits of our computational method were tested by calculating the phase transition temperatures and their associated enthalpies, and the derived figures compare favorably with the values determined experimentally.