New Coordination Polymers of Copper(I) and Silver(I) with Pyrazine and Piperazine: A Step Toward "Green" Chemistry and Optoelectronic Applications.

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-(CF3)2Pz]- ([PzF]-) besides Pyz or Ppz, whereas the sixth had the neutral diimine as a single chromophore. Complexes 1-3 are isomers of the same Cu/PzF/Pyz composition with the same or different unit cell stoichiometry, namely, {Cu6[3,5-(CF3)2Pz]6(Pyz)3(CH2Cl2)}∞ (1·CH2Cl2), {Cu2[3,5-(CF3)2Pz]}2(Pyz)2·toluene}∞ (2·toluene), and {Cu3[3,5-(CF3)2Pz]3(Pyz)1.5·1.5benzene}∞ (3·1.5benzene), respectively. Altering only the metal attains {Ag6[3,5-(CF3)2Pz]6(Pyz)2·2benzene} (4·2benzene), while also changing the neutral diimine attains {Ag2[3,5-(CF3)2Pz]2(Ppz)}∞ (5). Using Pyz without an anionic imine yields {[Cu(Pyz)(MeCN)2][BF4]}∞ (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 m2/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.

Trinuclear copper(I) and silver(I) adducts of 4-chloro-3,5-bis(trifluoromethyl)pyrazolate and 4-bromo-3,5-bis(trifluoromethyl)pyrazolate.

Syntheses, structural, and photoluminescence properties of {[4-X-3,5-(CF3)2Pz]M}3 (X = Cl or Br, M = Cu or Ag) containing a heavier halide at the pyrazolyl ring 4-positions are reported. The Cu2O and Ag2O react with [4-Cl-3,5-(CF3)2Pz]H or [4-Br-3,5-(CF3)2Pz]H to form the corresponding metal pyrazolates, which are trinuclear adducts of the type {[4-X-3,5-(CF3)2Pz]M}3 with a nine-membered M3N6 metallacyclic core. They also feature relatively short M···Cl or M···Br intertrimer separations (∼ 3.6 Å) leading to supramolecular aggregates in the solid state. Distinct from the 4-H analogues {[3,5-(CF3)2Pz]M}3, none of the four complexes described herein exhibits short intertrimer metal-metal interactions (as closest such M···M separations are at a distance greater than 5.0 Å). The {[4-X-3,5-(CF3)2Pz]M}3 adducts exhibit bright photoluminescence even at room temperature. The photophysical data suggest that the {[4-X-3,5-(CF3)2Pz]Cu}3 complexes emit from an associative excited state, and the drastic Stokes shift suggests a significant change to the ground state structure of the trinuclear moiety and/or intermolecular interactions upon photoexcitation. The {[4-X-3,5-(CF3)2Pz]Ag}3 complexes emit from a ligand-centered excited state affected by silver and the heavier halogens. Thin films of {[4-X-3,5-(CF3)2Pz]Cu}3 trimers are promising for volatile organic compound (VOC) sensor applications as they exhibit luminescence color change upon exposure to vapors of benzene and its alkylated derivatives.

On/off luminescence vapochromic selective sensing of benzene and its methylated derivatives by a trinuclear silver(I) pyrazolate sensor.

{[3,5-(CF(3))(2)Pz]Ag}(3) (1) films exhibit selective/reversible sensing of small-organic-molecule (SAM) vapors, which readily switch-on bright-green (benzene or toluene) or bright-blue (mesitylene) luminescence that switches-off upon vapor removal. Vapors of electron-deficient SAMs or non-aromatic solvents did not attain luminescence switching and were not adsorbed.

Structure and luminescence properties of a well-known macrometallocyclic trinuclear Au(I) complex and its adduct with a perfluorinated fluorophore showing cooperative anisotropic supramolecular interactions.

The structure and luminescence properties of a well-known trinuclear Au(i) imidazolate complex are determined for the first time along with its interaction with the organic π acid perfluoronaphthalene in the solid state and solution.

Golden metallopolymers with an active T(1) state via coordination of poly(4-vinyl)pyridine to pentahalophenyl-gold(I) precursors.

Brightly phosphorescent gold-based metallopolymers have been synthesized by reaction of nonluminescent reactants comprised of the commercially available polymer PVP = poly(4-vinylpyridine) and the Au(I) precursors [Au(C(6)X(5))THT] (X = F or Cl; THT = tetrahydrothiophene). The metallopolymer products exhibit remarkable photoluminescence properties including high solid-state quantum yield (up to 0.63 at RT) and coarse- and fine-tuning to multiple phosphorescence bands across the visible spectrum via luminescence thermochromism and site-selective excitation. The emissions are caused by intrachain and interchain aurophilic interactions between the linear Au(I) complexes in the metallopolymers. This investigation provides further manifestations of interesting chemistry and photophysics in N-heterocyclic coordination compounds of Au(I) by expansion from the small-molecule to the metallopolymer regime. The spectroscopic and material properties of the new class of metallopolymers are desirable for future studies that will utilize them as emitters for photonic applications such as polymer light-emitting diodes and sensors.

Metal effect on the supramolecular structure, photophysics, and acid-base character of trinuclear pyrazolato coinage metal complexes.

Varying the coinage metal in cyclic trinuclear pyrazolate complexes is found to significantly affect the solid-state packing, photophysics, and acid-base properties. The three isoleptic compounds used in this study are [[3,5-(CF3)2Pz]M]3 with M = Cu, Ag, and Au (i.e., Cu3, Ag3, and Au3, respectively). They form isomorphous crystals and exist as trimers featuring nine-membered M3N6 rings with linear two-coordinate metal sites. On the basis of the M-N distances, the covalent radii of two-coordinate Cu(I), Ag(I), and Au(I) were estimated as 1.11, 1.34, and 1.25 angstroms, respectively. The cyclic [[3,5-(CF3)2Pz]M]3 complexes pack as infinite chains of trimers with a greater number of pairwise intertrimer M...M interactions upon proceeding to heavier coinage metals. However, the intertrimer distances are conspicuously short in Ag3 (3.204 angstroms) versus Au3 (3.885 angstroms) or Cu3 (3.813 angstroms) despite the significantly larger covalent radius of Ag(I). Remarkable luminescence properties are found for the three M3 complexes, as manifested by the appearance of multiple unstructured phosphorescence bands whose colors and lifetimes change qualitatively upon varying the coinage metal and temperature. The multiple emissions are assigned to different phosphorescent excimeric states that exhibit enhanced M...M bonding relative to the ground state. The startling luminescence thermochromic changes in crystals of each compound are related to relaxation between the different phosphorescent excimers. The trend in the lowest energy phosphorescence band follows the relative triplet energy of the three M(I) atomic ions. DFT calculations indicate that [[3,5-(R)2Pz]M]3 trimers with R = H or Me are bases with the relative basicity order Ag << Cu < Au while fluorination (R = CF3) renders even the Au trimer acidic. These predictions were substantiated experimentally by the isolation of the first acid-base adduct, [[Au3]2:toluene]infinity, in which a trinuclear Au(I) complex acts as an acid.

External heavy-atom effect of gold in a supramolecular acid-base pi stack.

The nucleophilic trinuclear Au(I) ring complex Au3(p-tolN=COEt)3, 1, forms a sandwich adduct with the organic Lewis acid octafluoronaphthalene, C10F8. The 1.C10F8 adduct has a supramolecular structure consisting of columnar interleaved 1 ratio 1 stacks in which the Au3(p-tolN=COEt)3 pi-base molecules alternate with the octafluoronaphthalene pi-acid molecules with distances between the centroid of octafluoronaphthalene to the centroid of 1 of 3.458 and 3.509 A. The stacking with octafluoronaphthalene completely quenches the blue photoluminescence of Au3 (p-tolN=COEt)3, which is related to inter-ring Au-Au bonding, and leads to the appearance of a bright yellow emission band observed at room temperature. The structured profile, the energy, and the lifetime indicate that the yellow emission of the 1.C10F(8) adduct is due to monomer phosphorescence of the octafluoronaphthalene. The 3.5 ms lifetime of the yellow emission of 1.C10F8 is two orders of magnitude shorter than the lifetime of the octafluoronaphthalene phosphorescence, thus indicating a strong gold heavy-atom effect. The diffuse-reflectance spectrum of the solid adduct shows new absorptions that are red-shifted from the absorptions of the monomeric organic and inorganic components alone, indicating charge transfer. Luminescence excitation spectra suggest that these new absorptions represent the major excitation route that leads to the yellow luminescence of 1.C10F8, which is different from the conventional heavy-atom effect in which the phosphorescence route entails simply the enhancement of the S1-T1 intersystem crossing of the organic compound.

Brightly phosphorescent trinuclear copper(I) complexes of pyrazolates: substituent effects on the supramolecular structure and photophysics.

Synthetic details, solid-state structures, and photophysical properties of a group of trimeric copper(I) complexes containing pyrazolate ligands are described. The reaction of copper(I) oxide and the fluorinated pyrazoles [3-(CF(3))Pz]H, [3-(CF(3)),5-(Me)Pz]H, and [3-(CF(3)),5-(Ph)Pz]H leads to the corresponding trinuclear copper(I) pyrazolates, {[3-(CF(3))Pz]Cu}(3), {[3-(CF(3)),5-(Me)Pz]Cu}(3), and {[3-(CF(3)),5-(Ph)Pz]Cu}(3), respectively, in high yield. The {[3,5-(i-Pr)(2)Pz]Cu}(3) compound was obtained by a reaction between [Cu(CH(3)CN)(4)][BF(4)], [3,5-(i-Pr)(2)Pz]H, and NEt(3). These compounds as well as {[3,5-(Me)(2)Pz]Cu}(3) and {[3,5-(CF(3))(2)Pz]Cu}(3) adopt trimeric structures with nine-membered Cu(3)N(6) metallacycles. There are varying degrees and types of intertrimer Cu...Cu interactions. These contacts give rise to zigzag chains in the fluorinated complexes, {[3-(CF(3))Pz]Cu}(3), {[3-(CF(3)),5-(Me)Pz]Cu}(3), {[3-(CF(3)),5-(Ph)Pz]Cu}(3), and {[3,5-(CF(3))(2)Pz]Cu}(3), whereas the nonfluorinated complexes, {[3,5-(Me)(2)Pz]Cu}(3) and {[3,5-(i-Pr)(2)Pz]Cu}(3) form dimers of trimers. Out of all the compounds examined in this study, {[3-(CF(3)),5-(Ph)Pz]Cu}(3) has the longest (3.848 Angstroms) and {[3,5-(Me)(2)Pz]Cu}(3) has the shortest (2.946 Angstroms) next-neighbor intertrimer Cu...Cu distance. The Cu...Cu separations within the trimer units do not vary significantly (typically 3.20-3.26 Angstroms). All of these trinuclear copper(I) pyrazolates show bright luminescence upon exposure to UV radiation. The luminescence bands are hugely red-shifted from the corresponding lowest-energy excitations, rather broad, and unstructured even at low temperatures, suggesting metal-centered emissions owing to intertrimer Cu...Cu interactions that are strengthened in the phosphorescent state. The {[3-(CF(3)),5-(Ph)Pz]Cu}(3) compound exhibits an additional highly structured phosphorescence with a vibronic structure corresponding to the pyrazolyl (Pz) ring. The luminescence properties of solids and solutions of the trimeric compounds in this study show fascinating trends with dramatic sensitivities to temperature, solvent, concentration, and excitation wavelengths.

Blue phosphors of dinuclear and mononuclear copper(I) and silver(I) complexes of 3,5-bis(trifluoromethyl)pyrazolate and the related bis(pyrazolyl)borate.

The synthesis, structure, and photoluminescence properties are described for the three-coordinate mononuclear and dinuclear complexes [H(2)B(3,5-(CF(3))(2)Pz)(2)]M(2,4,6-collidine), M(1)(), and [[3,5-(CF(3))(2)Pz]M(2,4,6-collidine)](2), M(2)(), respectively (M = Cu; Ag). The solids exhibit bright blue phosphorescence, at room temperature for the copper compounds and at 77 K for all compounds. Ag(1)(), Cu(1)(), and Cu(2)() exhibit blue pyrazole-based structured emissions with short phosphorescence lifetimes, 10(1)-10(2) micros, due to an internal heavy-metal effect. Meanwhile, Ag(2)() exhibits curious multiple excitation-dependent emissions.

Bright phosphorescence of a trinuclear copper(I) complex: luminescence thermochromism, solvatochromism, and "concentration luminochromism".

A photophysical study is reported for the trinuclear copper(I) complex {[3,5-(CF3)2Pz]Cu}3. The neutral compound exhibits multicolor bright phosphorescent emissions both in the solid state and in solution. The emission can be tuned to multiple visible colors by controlling the temperature, solvent, and {[3,5-(CF3)2Pz]Cu}3 concentration, giving rise to luminescence thermochromism, luminescence solvatochromism, and a new optical phenomenon called "concentration luminochromism", respectively.

19F, (1)H-HOESY and PGSE NMR studies of neutral trinuclear complexes of Au(I) and Hg(II): evidence for acid-base stacking in solution.

By combining the information from 19F, 1H-HOESY and PGSE NMR methodologies, unprecedented direct evidence has been obtained for the formation of supramolecular assemblies in solution between the trinuclear cyclic AuI basic compounds ([Au(mu-C2,N3-bzim)]3 (bzim = 1-benzylimidazolate), 1, and [Au(mu-C,N-C(OEt)=N-p-C6H4-CH3)]3, 2, on one hand, and the trinuclear cyclic HgII acid complex [Hg(mu-C,C-C6F4)]3, 3, on the other hand. HOESY experiments indicate that a stacking similar to that observed in the solid state occurs. PGSE studies demonstrate the presence of an equilibrium between the free trinuclear entities and adduct A in the case of 2/3 admixtures (see Sketch) while for 1/3 admixtures, adducts A and B are mainly present in solution.