Design and Synthesis of Calixarene-Based Bis-alkynyl-Bridged Dinuclear AuIIsonitrile Complexes as Luminescent Ion Probes by the Modulation of Au⋅⋅⋅Au Interactions

Inducing Platinophilic Interactions in [Pt(SCN)4]2- Salts by Cation Tuning

A series of simple [Pt(SCN)4]2- salts with a variety of cations was synthesized and characterized using X-ray crystallography to determine factors that could induce platinophilic interactions between [Pt(SCN)4]2- anions, including cation size and shape, charge, and ability to participate in hydrogen bonding. The salts [N(PPh3)2]2[Pt(SCN)4], [AsPh4]2[Pt(SCN)4], and [Co(1,10-phenanthroline)3][Pt(SCN)4] feature bulky, noncoordinating cations where the [Pt(SCN)4]2- anions are completely separated from each other, with no Pt-Pt interactions present. Salts containing the hydrogen-bonding cations [Co(NH3)6]2[Pt(SCN)4]3 and [Co(en)3]2[Pt(SCN)4]3 (en = 1,2-ethylenediamine) display close Pt-Pt distances, with both compounds exhibiting platinophilic interactions with distances of 3.373(2) and 3.539(8) Å, respectively, the first reported platinophilic interactions with the [Pt(SCN)4]2- unit. [Co(en)3]2[Pt(SCN)4]3 also presents intermolecular chalcogen S···S and Pt···S interactions, resulting in increased dimensionality while also assisting in assembling the platinophilic interaction. The compounds are emissive at 77 K in the solid state, exhibiting a d-d metal-centered transition regardless of whether or not any platinophilic interactions are present. Overall, hydrogen-bonding cations are most likely to promote close proximity of the Pt(II) metal centers and induce the formation of platinophilic interactions in [Pt(SCN)4]2-.

Chloride Binding Properties of a Macrocyclic Receptor Equipped with an Acetylide Gold(I) Complex: Synthesis, Characterization, Reactivity, and Cytotoxicity Studies

In this work, we report the synthesis and characterization of a mono-nuclear “two wall” aryl-extended calix[4]pyrrole receptor (2Au) decorated with an acetylide-gold(I)-PTA complex at its upper rim. We describe the 1H NMR titration experiments of 2Au and its “two wall” aryl-extended calix[4]pyrrole synthetic precursors: the non-symmetric mono-iodo-mono-ethynyl 2 and the symmetric bis-iodo 3 with TBACl in dichloromethane and acetone solution. In acetone solution, we use isothermal titration calorimetry (ITC) experiments to thermodynamically characterize the formed 1:1 chloride complexes and perform pair-wise competitive binding experiments. In both solvents, we measured a decrease in the binding constant of the mono-nuclear 2Au complex for chloride compared to the parent mono-iodo-mono-ethynyl 2. In turn, receptor 2 also shows a reduction in binding affinity for chloride compared to its precursor bis-iodo calix[4]pyrrole 3. The free energy differences (∆G) of the 1:1 chloride complexes cannot be exclusively attributed to their dissimilar electrostatic surface potential values either at the center of the meso-phenyl wall or its para-substituent. We conclude that solvation/desolvation processes play an important role in the stabilization of the chloride complexes. In acetone solution and in the presence of TBACl, 6Au, a reference compound for the acetylide Au(I)•PTA unit, produces a bis(alkynyl)gold(I) anionic complex [7Au]−. Thus, the observation of two separate sets of signals for the bound aromatic calix[4]pyrrole protons, when more than 1 equiv. of the salt is added, is assigned to the formation of the chloride complexes of 2Au and of the “in situ” formed calix[4]pyrrole anionic dimer [8Au]−. Finally, preliminary data obtained in cell viability assays of 2Au and 6Au with human cancer cells lines assign them with moderate activities showing that the calix[4]pyrrole unit is not relevant.

Luminescent Behavior of Liquid–Crystalline Gold(I) Complexes Bearing a Carbazole Moiety: Effects of Substituent Bulkiness

Organometallic materials that exhibit white luminescence in condensed phases are of considerable interest for lighting and display applications. Herein, new carbazole-based Au(I) complexes containing an isocyanide group and a long pentyl chain were synthesized. The complex with an unsubstituted carbazole moiety exhibited a white emission at room temperature as well as nematic liquid crystalline behavior. Color tunability from white to blue was achieved when bulkier substituents were introduced at the 3 and 6 positions of the carbazole moiety. Furthermore, all complexes possessed long phosphorescence lifetimes in the crystal state. The proposed design framework provides new opportunities for practical applications using luminescent organometallic molecules.

Aurophilic Interactions in Multi-Radical Species: Electronic-Spin and Redox Properties of Bis- and Tris-[(Nitronyl Nitroxide)-Gold(I)] Complexes with Phosphine-Ligand Scaffolds

Multinuclear Au^I complexes with two or three nitronyl nitroxide-2-ide radical anion and phosphine-ligand scaffolds, (NN-Au)₂ -1 o, (NN-Au)₂ -1 m, and (NN-Au)₂ -1 p, have been synthesized to investigate the influence of Au^I -Au^I (aurophilic) interactions on the properties of multispin molecular systems. The desired complexes were successfully prepared in moderate yields in a one-pot synthesis from the corresponding phosphine ligand, Au^I source, parent NN, and sodium hydroxide. Among the prepared complexes, (NN-Au)₂ -1 o, in which an aurophilic interaction was clearly observed by crystal structure analysis, showed characteristic spin-spin interactions, electrochemical properties, and solvatochromic behavior. The results from theoretical calculations also suggested that the differences in properties between complex (NN-Au)₂ -1 o and the other complexes are due to intramolecular aurophilic interactions.

Tripodal gold(i) polypyridyl complexes and their Cu+ and Zn2+ heterometallic derivatives. Effects on luminescence

Three gold(i) tripodal complexes containing the tris(2-pyridylmethyl)amine (TPA) ligand coordinated to Au-PR₃ moieties (PR₃ = 1,3,5-triaza-7-phosphatricyclo[3.3.1.13.7]decane, PTA (1), 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane, DAPTA (2) and triphenylphosphane (3)) were prepared together with a cage-like structure containing triphosphane 1,1,1-tris(diphenylphosphinomethyl)ethane (4). The luminescence of these complexes has been studied and they show a red shift upon the formation of heterometallic complexes by reaction with Zn(NO₃)₂, CuCl and [Cu(CH₃CN)₄]BF₄. The different coordination motifs of the Zn²⁺ and Cu⁺ heterometallic species and the resulting changes in the recorded absorption, emission and NMR spectra were analysed and supported by TD-DFT calculations.

Synthesis, characterization, and antimicrobial activities of novel double-armed benzo-15-crown-5 and their sodium and potassium complexes

New aldehyde- and halogen- (Cl, Br, I) substituted double-armed benzo-15-crown-5 derivatives are synthesized by the reactions of 4′,5′-bis(bromomethyl)benzo-15-crown-5 with 5-chlorosalicylaldehyde, 5-bromosalicylaldehyde, or 5-iodosalicylaldehyde. The sodium and potassium complexes are obtained by reaction of crown ether with sodium perchlorate and potassium iodide, respectively. Novel Schiff base compounds containing three groups of benzo-15-crown-5 are obtained from the condensation of aldehydes with 4′-aminobenzo-15-crown-5. The structures of all compounds are elucidated by elemental analysis, 1H, 13C NMR, IR, and mass spectra. The antifungal and antibacterial effects of the synthesized ligands are evaluated against pathogenic microorganisms and show varying degrees of inhibitory effects against the growth of different pathogenic strains.

Graphical abstract

Controlling the supramolecular polymerization of dinuclear isocyanide gold(i) arylethynylene complexes through tuning the central π-conjugated moiety

Tuning the middle chromophores of dinuclear gold(i) arylethynyl complexes has been demonstrated to exhibit a pronounced effect on the photophysical properties, self-assembly mechanisms and morphologies.

Dinuclear metal complexes: multifunctional properties and applications

Dinuclear metal complexes have enabled breakthroughs in OLEDs, photocatalytic water splitting and CO₂reduction, DSPEC, chemosensors, biosensors, PDT and smart materials.

Calixarene-based alkynyl-bridged gold(i) isocyanide and phosphine complexes as building motifs for the construction of chemosensors and supramolecular architectures

A calixarene-based alkynyl-bridged Au(i) isocyanide complex with a triazolyl group as a receptor site has been synthesized and demonstrated to be a selective chemosensor for Zn²⁺ based on Au(i)⋯Au(i) interactions.

Cooperative supramolecular polymerization of phosphorescent alkynyl-gold(i)–isocyanide complexes

In this work, coil–rod–coil organogold(i) complexes have been successfully assembled into supramolecular polymers with green phosphorescent emission signal.

Rise of Conjugated Poly-ynes and Poly(Metalla-ynes): From Design Through Synthesis to Structure-Property Relationships and Applications

Conjugated poly-ynes and poly(metalla-ynes) constitute an important class of new materials with potential application in various domains of science. The key factors responsible for the diverse usage of these materials is their intriguing and tunable chemical and photophysical properties. This review highlights fascinating advances made in the field of conjugated organic poly-ynes and poly(metalla-ynes) incorporating group 4-11 metals. This includes several important aspects of conjugated poly-ynes viz. synthetic protocols, bonding, electronic structure, nature of luminescence, structure-property relationships, diverse applications, and concluding remarks. Furthermore, we delineated the future directions and challenges in this particular area of research.

Synthesis, photophysical properties and cation-binding studies of bipyridine-functionalized gold(i) complexes

A new family of Au(i) complexes equipped with bipyridine function demonstrate bright luminescence response to M(ii) cations in solution.

Cooperative self-assembly and gelation of organogold(i) complexes via hydrogen bonding and aurophilic Au⋯Au interactions

Organogold(i)-based fibers and gels have been successfully constructed, which involve Au⋯Au interactions in the self-assembled structures.

“Host–guest” binding of a luminescent dinuclear Au(i) complex based on cyclic diphosphine with organic substrates as a reason for luminescence tuneability

A dinuclear Au(i) complex with cyclic diphosphine is a versatile platform for different luminescence responses to nucleophilic and electrophilic molecules in solutions.

Synthesis and cation-binding studies of gold(i) complexes bearing oligoether isocyanide ligands with ester and amide as linkers

Bis(alkynyl)calix[4]arene gold(i) isocyanide complexes with amide linkers show strong binding affinity towards Al³⁺, which turns on the low-energy emission associated with the presence of Au(i)⋯Au(i) interactions.

Luminescent cation sensors: from host–guest chemistry, supramolecular chemistry to reaction-based mechanisms

This highlight provides a brief overview on luminescent cation detection strategies derived from a wide variety of organic and organometallic architectures, including those based on the ion-receptor complementarity, integrated with the extension of the concept of supramolecular chemistry and those using the irreversible analyte-specific reactions.

Synthesis, characterization, photophysics, and anion binding properties of gold(i) acetylide complexes with amide groups

A mononuclear gold(i) acetylide complex with an amide group, 3a, shows a dramatic color change upon addition of F⁻ in DMSO.

Highly Ag+ selective tripodal gold(I) acetylide-based "off-on" luminescence chemosensors based on 3(ππ*) emission switching

Newly prepared gold(I) acetylide-based luminescent cation sensors 1c and 1d, which bear a novel three-armed flexible conformation, together with control molecule 2c, were synthesized in four steps. 1c and 1d exhibit the π → π* absorption of the acetylide ligands in fluid solutions and produce the (3)(ππ*) emission of the acetylide ligands in the solid state and degassed THF solution. The (3)(ππ*) emission of 1c in DMSO can be turned on upon addition of Ag(+). The binding ratio between 1c and Ag(+) as well as the binding constant log K were determined as 1:1 and 4.35 ± 0.12 respectively by UV-vis titration experiments. The formation of [1c·Ag](+) adduct, which leads to the appearance of new up-field peaks, was confirmed by (1)H NMR spectroscopic titrations. The control (1)H NMR titration experiments for the acetylide-free analogue 1a and single-armed analogue 2c indicate the acetylide groups and tripodal structures are responsible for the binding of Ag(+). The control experiment for tripodal gold(I) acetylide analogue 1d suggests the change of PPh3 with P(2-Py)Ph2 induces similar binding affinity toward Ag(+) but less selectivity toward Ag(+). Free 1c also exhibits the anion binding affinity toward F(-), but the Ag(+) adduct [1c·Ag](+) shows less affinity toward F(-).

Photofunctional organometallics—from fundamentals to design, assembly and functions

A number of soluble platinum(II) and gold(I) complexes have been designed and synthesized. Their luminescence and photophysical behavior have been studied. Their assembly properties, which were governed by the noncovalent metal–metal interactions, have also been investigated with the introduction of various external stimuli. The UV–vis and emission spectral changes of these complexes, which arose from the modulation of their assembly and disassembly behavior, have demonstrated the establishment of a convenient and sensitive detection strategy for various types of analytes. These studies suggested the potential applications of these metal complexes as detection probes for a diverse range of target substrates.