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Structural Tuning of Anion‐Templated Motifs with External Stimuli through Crystal‐to‐Crystal Transformation
Author(s) -
Singh Ashutosh S.,
Tiwari Ranjay K.,
Lee Mandy M.,
Behera Jogendra N.,
Sun ShihSheng,
Chandrasekhar V.
Publication year - 2017
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.201604542
Subject(s) - chemistry , protonation , hydrogen bond , crystal structure , cycloaddition , photochemistry , crystallography , adduct , dissociation (chemistry) , crystal (programming language) , ion , molecule , organic chemistry , catalysis , computer science , programming language
Protonation of trans ‐1,2‐bis(4‐pyridyl)ethylene (4,4′‐bpe) with dilute sulfuric acid (33 %) afforded a protonated adduct [{4,4′‐bpe⋅2 H + } 2 {HSO 4 } −2 {SO 4 } −2 {H 2 O} 2 ] ( 1 ). The neighboring olefinic bond in 1 is in a suitable range (3.931–4.064 Å) to undergo a photochemical [2+2] cycloaddition reaction. Upon irradiation with UV light (365 nm), 1 undergoes a molecular sliding involving the 4,4′‐bpe⋅2 H + units, affording 2 , stabilized through O SO4 ⋅⋅⋅π interactions. Heating 1 to 50° C leads to a 3D hydrogen‐bonded organic framework (HOF) ( 3 ). This process occurs through thermal dissociation of the bisulfate anion. Diffusion of iodine through the crystal lattice of 1 and 3 enables the reduction of sulfate to bisulfate, affording a 1D hydrogen‐bonded chain ( 4 ). Solid‐state 13 C CPMAS NMR, IR, DSC, and powder XRD studies further support stimuli‐responsive structural tuning through crystal‐to‐crystal transformation. All these conversions occur with significant translational and rotational movements along with a series of bond‐breaking and bond‐forming processes.