Outer-shell s 0 /p 0 orbital mixing with d 10 orbitals and symmetry reduction upon cupriphication of cyclic trinuclear trigonal-planar gold(I) complexes are found to sensitize ground-state Cu(I)-Au(I) covalent bonds and near-unity phosphorescence quantum yields. Heterobimetallic Au 4 Cu 2 {[Au 4 (μ-C 2 ,N 3 -EtIm) 4 Cu 2 (μ-3,5-(CF 3 ) 2 Pz) 2 ], (4a)}, Au 2 Cu {[Au 2 (μ-C 2 ,N 3 -BzIm) 2 Cu(μ-3,5-(CF 3 ) 2 Pz)], (1) and [Au 2 (μ-C 2 , N 3 -MeIm) 2 Cu(μ-3,5-(CF 3 ) 2 Pz)], (3a)}, AuCu 2 {[Au(μ-C 2 ,N 3 -MeIm)Cu 2 (μ-3,5-(CF 3 ) 2 Pz) 2 ], (3b) and [Au(μ-C 2 ,N 3 -EtIm)Cu 2 (μ-3,5-(CF 3 ) 2 Pz) 2 ], (4b)} and stacked Au 3 /Cu 3 {[Au(μ-C 2 ,N 3 -BzIm)] 3 [Cu(μ-3,5-(CF 3 ) 2 Pz)] 3 , (2)} form upon reacting Au 3 {[Au(μ-C 2 ,N 3 -(N-R)Im)] 3 ((N-R)Im = imidazolate; R = benzyl/methyl/ethyl = BzIm/MeIm/EtIm)} with Cu 3 {[Cu(μ-3,5-(CF 3 ) 2 Pz)] 3 (3,5-(CF 3 ) 2 Pz = 3,5-bis(trifluoromethyl)pyrazolate)}. The crystal structures of 1 and 3a reveal stair-step infinite chains whereby adjacent dimer-of-trimer units are noncovalently packed via two Au(I)⋯Cu(I) metallophilic interactions, whereas 4a exhibits a hexanuclear cluster structure wherein two monomer-of-trimer units are linked by a genuine d 10 -d 10 polar-covalent bond with ligandunassisted Cu(I)-Au(I) distances of 2.8750(8) Å each-the shortest such an intermolecular distance ever reported between any two d 10 centers so as to deem it a "metal-metal bond" vis-à-vis "metallophilic interaction." Density-functional calculations estimate 35-43 kcal/mol binding energy, akin to typical M-M single-bond energies. Congruently, FTIR spectra of 4a show multiple far-IR bands within 65-200 cm −1 , assignable to v Cu-Au as validated by both the Harvey-Gray method of crystallographic-distance-to-force-constant correlation and dispersive density functional theory computations. Notably, the heterobimetallic complexes herein exhibit photophysical properties that are favorable to those for their homometallic congeners, due to threefold-to-twofold symmetry reduction, resulting in cuprophilic sensitization in extinction coefficient and solid-state photoluminescence quantum yields approaching unity (Φ PL = 0.90-0.97 vs. 0-0.83 for Au 3 and Cu 3 precursors), which bodes well for potential future utilization in inorganic and/or organic LED applications. Here, we show that outer 4s/p (Cu I ) and 6s/p (Au I ) orbitals can admix with the respective valence 3d and 5d orbitals to sensitize a bona fide polar-covalent metal-metal bond between two d 10 centers manifest by two rather short, 2.8750(8) Å, Cu(I)-Au(I) bonds without any ligand-bite-size assistance. The reduced symmetry in this family of complexes is also shown to impart higher extinction coefficients and phosphorescence quantum yields than those attained by the parent homometallic precursor complexes.Heterometallic complexes are remarkable molecules owing to their unique catalytic and optoelectronic properties (2, 3). Heterometallic species involving coinage metals have received immense attention owing to their fascinating structural a...

This work describes the reaction of a cyclic trinuclear complex, {[3,5-(CF 3 ) 2 Pz]Cu} 3 , with internal alkynes to construct di-and tetranuclear copper(I) complexes with short cuprophilic contacts and the study of their intriguing bonding and photophysical properties, both experimentally and theoretically. For comparison, we have also investigated the related copper(I) trifluoroacetate 3-hexyne complexes so as to deduce and isolate the role played by the supporting pyrazolate ligand on the luminescence of these and related complexes. Some adducts reported herein feature bridging (i.e., μ 2 −η 2 ,η 2 -) alkyne coordination modes, which is rare for copper(I)−alkyne complexes documented in the literature. Raman data show red shifts in the average υ ̅ CC stretching frequency from 2260 cm −1 in free 3-hexyne to 2050 cm −1 in the terminal η 2 -/2e-donor alkyne adduct Cu 2 (μ-[3,5-(CF 3 ) 2 Pz]) 2 (EtCCEt) 2 (1) and, more drastically, to 1874 cm −1 in the bridged μ 2 −η 2 ,η 2 -/4e-donor adduct Cu 4 (μ-[3,5-(CF 3 ) 2 Pz]) 4 (μ-EtCCEt) 2 (2). The tetranuclear 2-butyne adduct Cu 4 (μ-[3,5-(CF 3 ) 2 Pz]) 4 (μ-MeCCMe) 2 (3) also shows a large reduction in υ ̅ CC relative to that of free 2-butyne. The effects of strengthened copper-alkyne interactions in the bridging relative to terminal alkynes are also reflected in the CCC bending back angles. Photophysical studies in the solid state reveal the significance of the pyrazolate supporting ligand to bestow bright photoluminescence, which is found only for the pyrazolate-supported compounds 1−3 but not the trifluoroacetate copper-alkyne complexes Cu 2 (μ-CF 3 CO 2 ) 2 (EtCCEt) 2 (4) and Cu 4 (μ-CF 3 CO 2 ) 4 (μ-EtCCEt) 2 (5). The orange phosphorescence with ∼50 μs lifetime at room temperature in 1−3 thermochromically changes to generate additional green/yellow bands at cryogenic temperatures due to suppression of internal conversion from the respective T 2 → T 1 states in each solid, whereas solvent effects lead to additional blue-shifted bands in glassy solvent media. Computational analyses explains the bonding and spectral results and suggest that the major excited-state distortion is due to significant (≥20°) rotation of the alkyne ligands on Cu(I) in the di-or tetranuclear adducts, as opposed to excimeric contraction of cuprophilic Cu(I)••• Cu(I) distances. X-ray crystallographic data of 1−3 and 5 are also presented.

A novel luminescent azo-linked polymer (ALP) has been constructed from 1,3,6,8-tetra(4-aminophenyl)pyrene using a copper(I)-catalyzed oxidative homocoupling reaction. The polymer displays high porosity with a Brunauer–Emmett–Teller surface area of 1259 m 2 g –1 and narrow pore size distribution (1.06 nm) and is able to take up a significant amount of CO 2 (2.89 mmol g –1 ) at 298 K and 1.00 bar with a high isosteric heat of adsorption of 27.5 kJ mol –1 . Selectivity studies applying the ideal adsorbed solution theory revealed that the novel polymer has moderately good selectivities for CO 2 /N 2 (55.1) and CO 2 /CH 4 (10.9). Furthermore, the ALP shows fluorescence quenching in the presence of Hg 2+ , Pb 2+ , Tl + , and Al 3+ ions. Compared with these ions, the ALP showed no sensitivity to light metal ions such as Na + , K + , and Ca 2+ in ethanol–water solution, clearly indicating the high selectivity of the ALP toward heavy metal ions. The exceptional physiochemical stability, high porosity, and strong luminescence make this polymer an excellent candidate as a fluorescent chemical sensor for the detection of heavy metal ions.

Five coordination polymers and one hexanuclear cluster have been obtained, and their crystal structures were determined upon reaction of Cu(I) or Ag(I) precursors with pyrazine (Pyz) or piperazine (Ppz). Five complexes are mixed-imine-ligand with anionic-fluorinated pyrazolate [3,5-(CF)Pz] ([Pz]) besides Pyz or Ppz, whereas the sixth had the neutral diimine as a single chromophore. Complexes 1-3 are isomers of the same Cu/Pz/Pyz composition with the same or different unit cell stoichiometry, namely, {Cu[3,5-(CF)Pz](Pyz)(CHCl)} (1·CHCl), {Cu[3,5-(CF)Pz]}(Pyz)·toluene} (2·toluene), and {Cu[3,5-(CF)Pz](Pyz)·1.5benzene} (3·1.5benzene), respectively. Altering only the metal attains {Ag[3,5-(CF)Pz](Pyz)·2benzene} (4·2benzene), while also changing the neutral diimine attains {Ag[3,5-(CF)Pz](Ppz)} (5). Using Pyz without an anionic imine yields {[Cu(Pyz)(MeCN)][BF]} (6). The crystal structure of 1 shows two trimers linked together with two pyrazine ligands. Crystals of 2 represent a metal-organic framework (MOF-TW1) with significant surface area (1278 m/g) and porosity (23.7% void volume) without considering toluene adsorbates in channels. MOF-TW1 was obtained serendipitously upon a reaction attempt to attain a mixed-metal product, instead attaining a Cu(I)-only product with interconnected four-coordinate dinuclear units. Likewise, 3 was obtained through a transmetalation of all Ag atoms in 4 to replace them by Cu atoms. Three reactions (to obtain 1, 4, and 5) were successfully carried out by both solvent-mediated and solventless transformations, whereas 2 and 3 were obtained only by solvent-mediated reactions, while 6 was attainable only by solventless transformations. The solventless transformations occurred either by sublimation and vapor diffusion or by mechanical grinding at ambient laboratory conditions-without the aid of heating, high pressure, vacuum, or any automated equipment. All transformations could be monitored by the human eye as the reaction progresses, as evidenced by progressive discoloration and/or luminescence changes. All crystal structures were obtained with the aid of conventional crystal growth methods from organic solvents for bulk products obtained from both solvelntless and solvent-mediated reactions. Powder X-ray diffraction was used to compare bulk products with one another and the crystallographic products. All Cu(I) products are colored and nonluminescent; the progress of their vapor diffusion-based solventless reactions can be followed by gradual discoloration of white solid reactants and/or quenching precursor's phosphorescence. Both Ag(I) products were colorless with 4 being luminescent but not 5.