Two Thermochromic Layered Iodoargentate Hybrids Directed by 4- and 3-Cyanopyridinium Cations

Abstract

Two layered iodoargentates, [HCP][Ag 2 I 3 ] (HCP + = NH-4-cyanopyridinium) (1) and [MCP][Ag 4 I 5 ] (MCP + = N-methyl-3-cyanopyridinium) (2) have been solvothermally synthesized. For 1, the inorganic layer is built up by 4-connected Ag 4 I 8 unit with cubane-type Ag 4 I 4 core via sharing peripheral μ 2 -I in ab plane, while the HCP + cations are located at the apertures and interlayer space. For 2, the inorganic layer is constructed from [Ag 6 I 6 ] n and [AgI 3 ] n 2n− chains via alternative corner-and edge-sharing modes along the b-axis, while the MCP + cations lie between neighboring layers. Compounds 1 and 2 exhibit reducing band gaps relative to the bulk β-AgI and remarkable thermochromism, which are ascribed to the intermolecular charge transfer (CT) and affected by electron affinity of pyridinium cations.

Structurally dependent thermochromism of two iodoargentate hybrids based on the intermolecular charge transfer

“…Although the inorganic moieties in 1 and 2 have been reported, their bright yellow color attract our attention compared with the almost colorless iodoargentates directed by saturated organic cations [43,44,47,50e52] and suggest there exist organic-inorganic interaction in title compounds, which have been confirmed in our previous work [18,19] and encourage further investigation on their optical and thermochromic properties.…”

“…Obviously, increase of spatial size of SDAs not only lead to complication of bonding features in inorganic chains, but also to the changes of relative positions between organic and inorganic moieties, which can be found in other halometallate systems [41,47e49]. In addition, when the N-substituent is methyl group, we previously reported a 2D layered [MCP][Ag 4 I 5 ] (MCP ¼ N-alkylated 3-cyanopyridinium) [18]. In contrast to the serial N-alkylated 4-cyanopyridinium iodoargentates [19], structural irregularity of N-alkylated 3-cyanopyridinium iodoargentates suggests the unique effect of molecular symmetry of SDAs on the assembly of inorganic moieties, which is rarely mentioned [18,19,46].…”

“…Recently reported thermochromic iodoplumbates [7e10] and iodobismuthates [11,12] as well as photochromic chlorobismuthates [13e16] and iodoplumbates [17] exhibit interesting component-structure-property relationship. Comparatively, chromism based on organicinorganic iodoargentate hybrids is rarely reported [18,19].…”

“…Recently, we focused our attention on the synthesis and thermochromic characterization of pyridinium-directed iodoargentate hybrids and found that the thermochromism depends on the charge accepting ability of pyridinium cations (4-cyanopyridnium and 3-cyanopyridinium) [18,19]. As an extension of previous work, two as-synthesized iodoargentate hybrids, [(EC) (Ag 2 I 3 )] n (1) and [(PC) (Ag 5 I 6 )] n (2) directed by N-alkylated 3-cyanopyridiniums are prepared, and their optical and thermochromic properties are characterized.…”

Two viologen-based crystalline photoactive complexes constructed by zinc chloride and N-(3-cyanophenyl)-4,4′-bipyridinium units: Structural arrangement of donor–acceptor units and photoresponsive characteristics

“…Compound 2 shows an obvious decomposition at 370°C, corresponding to the leaving of CNPBPY organic ligand. Iodoargentate hybrid complexes with cyanopyridinium cations have been reported having remarkable thermochromism characters, which originated from intermolecular charge transfer (CT) [16]. By comparison, the two crystalline cyano substituted viologen-based materials here all exhibit stable photochromism characteristics from yellow to green upon exposure to light irradiation (xenon lamp, 150 W) (Fig.…”