Aggregation-Enhanced Room-Temperature Phosphorescence from Au(I) Complexes Bearing Mesogenic Biphenylethynyl Ligands

Gold(I) complexes, enabling to form linear coordination geometry, are promising materials for manifesting both aggregation-induced emission (AIE) behavior due to strong intermolecular Au–Au (aurophilic) interactions and liquid crystalline (LC) nature depending on molecular geometry. In this study, we synthesized several gold(I) complexes with rod-like molecular skeletons where we employed a mesogenic biphenylethynyl ligand and an isocyanide ligand with flexible alkoxyl or alkyl chains. The AIE behavior and LC nature were investigated experimentally and computationally. All synthesized gold(I) complexes exhibited AIE properties and, in crystal, room-temperature phosphorescence (RTP) with a relatively high quantum yields of greater than 23% even in air. We have demonstrated that such strong RTP are drastically changed depending on the crystal-size and/or crystal growth process that changes quality of crystals as well as the aggregate structure, of e.g., Au–Au distance. Moreover, the complex with longer flexible chains showed LC nature where RTP can be observed. We expect these rod-like gold(I) complexes to have great potential in AIE-active LC phosphorescent applications such as linearly/circularly polarizing phosphorescence materials.

Synthesis and coordination to the coinage metals of a trimethylpyrazolyl substituted 3-arylacetylacetone

The ligand 3-(4-(1,3,5-trimethyl-1H-pyrazol-4-yl)phenyl)acetylacetone (1) combines a Pearson hard O,O′ chelating acetylacetone donor with a softer pyrazole N donor bridged by a phenylene spacer. Deprotonation and coordination to CuII leads to a square planar bis-acetylacetonato complex; interpreting the close proximity of an adjacent complex’s pyrazole moiety as an η 2 ${{\eta}}^{2}$ coordination to the axial CuII position leads to a two dimensional extended structure. The N donor capabilities are proven by coordination to AgPF6 and AuCl; for AgI a cationic linear bis-pyrazole complex as a toluene solvate is obtained with toluene-pyrazole π-interactions and an essentially uncoordinated PF 6 - ${{\mathrm{PF}}_{6}}^{-}$ anion. In the case of AuCl a neutral linear coordination compound with one chlorido and one pyrazole ligand 1 is obtained. Comparing the dihedral angles with a closely related but shorter ligand reveals a larger rotational degree of freedom in 1, allowing for richer architectures in emerging coordination polymers.

A trigonal coordination of Au(I) phosphane complexes stabilized by O–H⋯X (X = Cl–, Br–, I–) interactions

In this work, we show that intramolecular hydrogen bonding can be used to stabilize tri-coordinated phosphane-gold(I) complexes. Two molecular structures of 2-(diphenylphosphino)benzoic acid (L) coordinated to a gold(I) atom were determined by single-crystal X-ray diffraction. The linear L–Au–Br shows a standard linear coordination and dimerizes via hydrogen bonds of the carboxylic acid. Upon addition of two additional phosphane ligands the complex [L3Au]X is formed which is stabilized by three intramolecular –C(O)O–H…X hydrogen bonds as proven by the X-ray structure of the respective chlorido-complex. X-ray powder diffractograms suggest the same structure also for X– = Br– and I–. Graphic abstract

Synthesis and Structural Characterization of a Silver(I) Pyrazolato Coordination Polymer

Coinage metal(I)···metal(I) interactions are widely of interest in fields such as supramolecular assembly and unique luminescent properties, etc. Only two types of polynuclear silver(I) pyrazolato complexes have been reported, however, and no detailed spectroscopic characterizations have been reported. An unexpected synthetic method yielded a polynuclear silver(I) complex [Ag(μ-L1Clpz)]n (L1Clpz− = 4-chloride-3,5-diisopropyl-1-pyrazolate anion) by the reaction of {[Ag(μ-L1Clpz)]3}2 with (nBu4N)[Ag(CN)2]. The obtained structure was compared with the known hexanuclear silver(I) complex {[Ag(μ-L1Clpz)]3}2. The Ag···Ag distances in [Ag(μ-L1Clpz)]n are slightly shorter than twice Bondi’s van der Waals radius, indicating some Ag···Ag argentophilic interactions. Two Ag–N distances in [Ag(μ-L1Clpz)]n were found: 2.0760(13) and 2.0716(13) Å, and their N–Ag–N bond angles of 180.00(7)° and 179.83(5)° indicate that each silver(I) ion is coordinated by two pyrazolyl nitrogen atoms with an almost linear coordination. Every five pyrazoles point in the same direction to form a 1-D zig-zag structure. Some spectroscopic properties of [Ag(μ-L1Clpz)]n in the solid-state are different from those of {[Ag(μ-L1Clpz)]3}2 (especially in the absorption and emission spectra), presumably attributable to this zig-zag structure having longer but differently arranged intramolecular Ag···Ag interactions of 3.39171(17) Å. This result clearly demonstrates the different physicochemical properties in the solid-state between 1-D coordination polymer and metalacyclic trinuclear (hexanuclear) or tetranuclear silver(I) pyrazolate complexes.

Transmembrane Transport of copper(I) by Imidazole-Functionalised Calix[4]arenes

Synthetic carriers for various cations and anions have been reported, but here we present the first synthetic Cu⁺ transporters. A series of calix[4]arenes with two imidazole groups has been developed and their bidentate linear coordination motif allows the selective extraction of Cu⁺ into chloroform. Transmembrane transport of Cu⁺ into liposomes was investigated with a newly developed assay and opens the way to the further development of Cu⁺ ionophores for biomedical applications.

Transmembrane Transport of copper(I) by Imidazole-Functionalised Calix[4]arenes

Synthetic carriers for various cations and anions have been reported, but here we present the first synthetic Cu⁺ transporters. A series of calix[4]arenes with two imidazole groups has been developed and their bidentate linear coordination motif allows the selective extraction of Cu⁺ into chloroform. Transmembrane transport of Cu⁺ into liposomes was investigated with a newly developed assay and opens the way to the further development of Cu⁺ ionophores for biomedical applications.

Transmembrane Transport of copper(I) by Imidazole-Functionalised Calix[4]arenes

Synthetic carriers for various cations and anions have been reported, but here we present the first synthetic Cu⁺ transporters. A series of calix[4]arenes with two imidazole groups has been developed and their bidentate linear coordination motif allows the selective extraction of Cu⁺ into chloroform. Transmembrane transport of Cu⁺ into liposomes was investigated with a newly developed assay and opens the way to the further development of Cu⁺ ionophores for biomedical applications.

Transmembrane Transport of copper(I) by Imidazole-Functionalised Calix[4]arenes

Synthetic carriers for various cations and anions have been reported, but here we present the first synthetic Cu⁺ transporters. A series of calix[4]arenes with two imidazole groups has been developed and their bidentate linear coordination motif allows the selective extraction of Cu⁺ into chloroform. Transmembrane transport of Cu⁺ into liposomes was investigated with a newly developed assay and opens the way to the further development of Cu⁺ ionophores for biomedical applications.

Supramolecular linear coordination polymers of human serum albumin and haemoglobin

Human serum albumin and human haemoglobin having two-terpyridyl arms were readily polymerized via a bis(terpyridyl)–Fe2+ complex to generate watersoluble, uniform, and linear nanofibres.