Self-Assembly of Silver(I) and Gold(I) N-Heterocyclic Carbene Complexes in Solid State, Mesophase, and Solution

Abstract

The assembly of silver(I) and gold(I) complexes of functionalized N-heterocyclic carbenes (NHCs) of the type [M(C(n),amide-imy)(2)][anion] were studied, in which C(n),amide-imy stands for an NHC of imidazol-2-ylidene having one N-alkyl substituent (C(n)H(2n+1)) and one N-acetamido substituent, while the anions are Br(-), NO(3)(-), BF(4)(-) or PF(6)(-). A single crystal X-ray diffraction study reveals that self-assembly of [Ag(C(10),amide-imy)(2)][PF(6)] through Coulombic, hydrogen bonding, and hydrophobic interactions gives a lamellar structure with tubular architecture around the metal ion head core. Self-assembly of these functionalized NHC complexes also leads to the formation of the first example of thermotropic liquid crystals of silver(I)-NHCs and gels of gold(I)-NHC. Results from an infrared spectroscopy study show that the degree of chain motion in the gel state is smaller than that in the mesophase, yet comparable to that in the solid state. In addition, the technique of nuclear magnetic resonance diffusion ordered spectroscopy was found for the first time to be a good tool to study the phase transition of gels. Xerogels of gold(I)-NHCs display fibers, oriental lantern-shaped bundles of belts and helical fibers when observed under scanning electron and transmission electron microscopes.

Inorganic–Organic Hybrid Surfactant Crystals: Structural Aspects and Functions

“…Here, the coordination mode does not mean accurate coordination geometry. There are six typical coordination and packing modes: asymmetric coordination of one single-chained ligand (Figure 4a) [38,39,55,61,65], symmetric coordination of two single-chained ligands lying on the opposite sides of the metal cation (Figure 4b) [41][42][43]49,51,53,55,59,60], symmetric coordination of one double-chained ligand with two chains at the opposite sides of the metal cation (Figure 4c) [45,47,54,55,62], asymmetric coordination of two single-chained ligands lying on the same side of the metal cation (Figure 4d) [44,46,48,56], asymmetric coordination of one double-chained ligand with narrow space between the chains (Figure 4e) [50,54,63], and asymmetric coordination of one double-chained ligand with wide space between the chains (Figure 4f) [41]. However, the essential feature is the formation of a layered structure that consists of M n+ inorganic layers and surfactant organic layers.…”

“…Thermal motion in the long amphiphilic chains plausibly affects the electronic spin state of metal cations. These crystals intrinsically can exhibit the phase transition to the liquid crystalline state with an increase in the temperature as metallomesogens [67], and their mesomorphic property has been investigated [41][42][43][44][45][46]51,68,69]. Ionic conductivity [70,71], photoluminescence [39,54,62,63], catalytic activity [47,48], thin-film formation ability [39,69], and behavior as preparative precursor for metal nanoparticles [43,57] have been explored recently.…”

Liquid crystals based on silver carbene complexes derived from dimeric bis(imidazolium) bromide salts

“…15 Moreover, a short-range nematic phase was evidenced for a bis(imidazolium) salt that posess four cyanobiphenyl mesogenic groups on each side, which is very 70 uncommon for ionic liquid crystals, in particular for ILC based on imidazolium cations. We succesfully proved that it is possible to prepare thermally stable silver-NHC complexes with liquid crystalline properties, with decomposition temperatures significantly higher than their 75 bis(imidazolium) precursors.…”

“…However, reports of liquid crystalline metal-NHC complexes derived from imidazolium 35 cations are few 11 and limited to metals such as Pd, 12 Au and Ag, 13 despite their remarkable thermal stability. While many Ag-NHC with different ways of assembling were reported, 14 only one LC system based on Ag-NHC having long alkyl chains was reported to date by Lin et al 15 These materials, generally, show a SmA 40 phase which is stable at temperatures above 100 o C and, in some cases, they show decomposition during isotropisation. We would like to show that by using appropriate mesogenic groups (cyanobiphenyl or cholesteryl groups) linked to a bis(imidazolium) fragment via flexible alkyl spacers can 45 successfully lead to thermally stable Ag-NHC complexes that show enantiotropic SmA phases at significantly lower temperatures, close to ambient temperatures.…”

AuI⋅⋅⋅AuI Interaction Assisted Host–Guest Interactions and Stimuli‐Responsive Self‐Assembly in Tetranuclear Alkynylgold(I) Calix[4]arene‐Based Isocyanide Complexes

“…[2] The Au I ···Au I distance is found to lie between 2.8-3.3 . [5][6][7][8][9][10] These intrinsic properties of gold(I) centers have been utilized in various studies to designi nteresting functional materials such as liquid crystals, [11] metallogels, [12] and organic light-emitting diodes. [5][6][7][8][9][10] These intrinsic properties of gold(I) centers have been utilized in various studies to designi nteresting functional materials such as liquid crystals, [11] metallogels, [12] and organic light-emitting diodes.…”