Two-Dimensional Silver-Thiocyanate Layers Directed by Viologens: Structural Transformations upon Low Pressure Stimuli, Piezochromic Luminescence, Photocurrent Responses, and Photocatalytic Properties

Abstract

The reactions of AgSCN with excess KSCN in the 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 the formula of [Ag4­(SCN)6] n 2n– and [Ag2(SCN)4] n 2n– are the scarce representative examples of the two-dimensional (2-D) polypseudorotaxane arrays penetrated (for 1–6) or intercalated (for 7) by viologen dications. Upon an external low pressure stimulus, the 2-D silver-thiocyanate layers penetrated by cations exhibit looser packing with longer Ag–S­(N) bond lengths, weaker charge transfer (CT) interactions, and larger cavities, but the contrary trend can be found on the compound with intercalated organic cations. Due to the strong CT interactions between viologens and silver-thiocyanate skeletons, the CTs can occur at room temperature. Interestingly, 7 represents typical reversible piezochromic luminescence behavior. 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 density functional theory calculations were executed to correlate their properties.

Encapsulating Halometallates into 3-D Lanthanide-Viologen Frameworks: Controllable Emissions, Reversible Thermochromism, Photocurrent Responses, and Electrical Bistability Behaviors

“…Therefore, due to the strong CT transitions and efficient transfer route, room temperature ESR singles can be monitored without an external stimulus, which have also be documented in metal pseudohalide/viologen hybrids. 79 The optical band gaps obtained by the extrapolation of the linear portion of the absorption edges are estimated to be 2.47, 2.39, 1.89, and 2.03 eV for 1−4, respectively, which are in accordance with their dark colors (Figure 5d). Compared with that of bulk PbI 2 (2.47−2.49 eV) 80 and BiI 3 itself (1.73 eV), 81 red-shifts for 1 and 2 and blue-shifts for 3 and 4 can be observed, which is in agreement with the conclusion that the energy band gaps of halometallate-based hybrids mainly derive from the charge transfer of the inorganic halide components.…”

“…In this work, the CT transition route is from lead/bismuth halide anions to bpdo ligands via hydrogen bonds (Table S4), and because of the coordination bonds between bpdo and Ln 3+ ions, the radicals move to Ln 3+ centers. Therefore, due to the strong CT transitions and efficient transfer route, room temperature ESR singles can be monitored without an external stimulus, which have also be documented in metal pseudohalide/viologen hybrids …”

A Series of Iodoargentates Directed by Solvated Metal Cations Featuring Uptake and Photocatalytic Degradation of Organic Dye Pollutants

“…Photocatalytic degradation technology is also an effective approach for the removal of dye pollutants. [52] Therefore, MV, which could be hardly adsorbed by the iodoargentate series via ion-exchange,w as selected as the test pollutant to assist the investigation of photocatalytic activity for 1-3.I ft here is with the absence of 1-3,n oo bviousr eduction in concentration for MV could be observedw ith time increasing and the degradation process is negligible upon visible light irradiation. Once samples 1-3 were put into the ethanol (for 1)o rD MSO (for 2 and 3)s olutionsc ontaining cationic MV molecules, the absorbance intensity in the UV-vis spectra decreased gradually as irradiation time with visible light increases.…”

A Three-Component Hybrid Templated by Asymmetric Viologen Exhibiting Visible-Light-Driven Photocatalytic Degradation on Dye Pollutant in Maritime Accident Seawater

“…Researchers have already developed numerous photocatalysts, including the traditional TiO 2 semiconductor materials [6], nano particles (ZnO, CdS, PbMoO 4 ) [7,8], g-C 3 N 4 or its composites [9], and inorganic/organic hybrids [10,11]. Among these photocatalysts, inorganic/organic hybrids are good photocatalysts because they are stable, efficient, and band-gap tunable [12,13], which can be achieved by the structural modification on their inorganic/organic moieties or their interactions. The Pb-based hybrids have demonstrated their photocatalysis activities on organic dyes, which stem from the synergism of all moieties [13,14].…”

“…Among these photocatalysts, inorganic/organic hybrids are good photocatalysts because they are stable, efficient, and band-gap tunable [12,13], which can be achieved by the structural modification on their inorganic/organic moieties or their interactions. The Pb-based hybrids have demonstrated their photocatalysis activities on organic dyes, which stem from the synergism of all moieties [13,14]. Iodobismuthate-based photocatalysts such as BiOI have also illustrated the visible light activities for removal of methylene blue [15][16][17][18].…”