2-D Silver-thiocyanate Layers Directed by Viologens: Structural Transformations upon Low Pressure Stimuli, Piezochromic Luminescence, Photocurrent Responses and Photocatalytic Properties

摘要： The reactions of AgSCN with excess KSCN in presence of linear viologens templates afford seven new hybrids, {(MV)[Ag4(SCN)6]}n (1), {(MV)[Ag2(SCN)4]}n (2), {(EV)[Ag4(SCN)6]}n (3), {(EV)[Ag2(SCN)4]}n (4), {(BV)[Ag4(SCN)6]}n (5), {(CMV)[Ag2(SCN)4]}n (6) and {(BMPE)[Ag2(SCN)4]}n (7), (MV2+=methyl viologen, EV2+=ethyl viologen, BV2+=benzyl viologen, CMV2+=cyanomethyl viologen, BMPE2+=1,2-bis(N-methylpyridiniim-4-yl)ethane). The silver-thiocyanate skeletons with formula of [Ag4(SCN)6]n 2n- and [Ag2(SCN)4]n 2n- are the scarce representative examples of the 2-D polypseudorotaxane arrays penetrated (for 1-6) or intercalated (for 7) by viologen dications. Upon the external low pressure stimulus, the 2-D silver-thiocyanate layers penetrated by cations exhibit loser packing with longer Ag-S(N) bond lengths, weaker CT interactions and larger cavities, but the contrary trend can be found on compound with intercalated organic cations. Due to the strong CT interactions between viologens and silver-thiocyanate skeletons, the charge transfers can occur at room temperature. Interestingly, 7 represents typical reversible piezochromic luminescence behaviour. In addition, they show excellent photocurrent responses and efficient photocatalytic degeneration performances on organic dyes. Finally, their band structures and density of states before and after compression based on DFT calculations were executed to correlate their properties.