Structural and Functional Modulation of Five 4-Cyanopyridinium Iodoargentates Built Up from Cubane-like Ag₄I₄ Nodes

Abstract

Five iodoargentate hybrids, {[MC][Ag 2 I 3 ]} n (1), {[EC][Ag 2 I 3 ]} n (2), {[PC] 2 [Ag 4 I 6 ]} n (3), {[BC] 2 [Ag 4 I 6 ]} n (4), and {[IPC] 2 [Ag 4 I 6 ]} n (5) (MC + = N-methyl-4-cyanopyridinium, EC + = N-ethyl-4-cyanopyridinium, PC + = N-propyl-4cyanopyridinium, BC + = N-butyl-4-cyanopyridinium, and IPC + = N-isopentyl-4-cyanopyridinium), have been solvothermally synthesized. Built up from μ-I bridging cubane-like Ag 4 I 4 nodes, 1 and 2 present similar two-dimensional grid-like layers with the MC + and EC + cations located at the apertures of inorganic layers and interlayer space, while 3, 4, and 5 possess threedimensional open frameworks with the PC + , BC + , and IPC + cations intercalated in the channels. 1−5 exhibit reducing band gaps with respect to the bulk β-AgI and interesting low temperature reversible thermochromism, which can be ascribed to the temperature effects directly on the population of intermolecular charge transfer. Variations in structure and property reveal delicate modulating effect of N-alkyl-4-cyanopyridinium cations and flexibility of iodoargentate frameworks.

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.…”

“…Each Ag atom is coordinated by three m 3 -I atoms and one m 5 -I atom to adopt a distorted tetrahedral geometry. The AgeI bond distances and the IeAgeI bond angles are 2.8103(6)e3.0642(6) Å and 90.212(16)e116.519 (19) , respectively. The Ag,,,Ag distances (3.1645 (7)e3.3298(7) Å) suggest the presence of argentophilic interactions.…”

“…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.…”