| Electron–rich metal halides as semiconductor material are ofwide interests in the field of functional materials. Especially, hybridhalometallites, due to their structural diversity and rich optical andelectronic properties, have attracted increasing attention, whichlargely depend on the structural and functional features ofcounterions. Herein, N–alkyl–cyanopyridinium iodoargentates wereselected as target compounds to study the structural regularity andband gap modulation, as well as reversible thermochromismoriginated from intermolecular charge transfer based on thecharacterization of single–crystal X–ray diffraction, IR, UV–vis forseven iodoargentate hybrids.Single crystal structure analysis reveal an regular variationbetween the N–alkylated cyanopyridinium cations and iodoargentateframeworks, as well as band gaps and thermochromism. For fiveN–alkyl–4–cyanopyridinium directed iodoargentate frameworks,common occurrence of cubane–like Ag4I4as secondary building unitshow the unique structural directing effects of4–cyanopyridinemotif. Corresponding to the lengthening of alkyl chain, dimensionalincrease of inorganic moieties exhibits delicate flexibility andexcellent structural matching for iodoargentate hybrids. However,for two N–alkyl–2–cyanopyridinium directed iodoargentates, obvious chainlike features and changes in connection modes are likely due tothe lower symmetry and space steric hindrance of2–cyanopyridine.UV–vis spectra and structural analysis demonstrate apparentexistence of intermolecular charge transfer in the title compoundsand remarkable red shift of band gaps relative to bulk β–AgI. Theircoloration and temperature induced chromism are not onlydependent on electron–accepting ability of cyanopyridinium, butalso affected by intrinsic stacking modes between organic andinorganic moieties, which exhibit interestingcomponent–structure–property relationship and can contribute tothe development and application of new functional materials. |
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