Structural, Photoluminescent and Theoretical Evidence for Ligand-unsupported Argentophilic Interactions in a Supramolecular Aggregate of [Ag_2(Hida)(NH_3)_2]

A new neutral [Ag2（Hida）（NH3）2] molecule （1, H3ida = 1H-imidazole-4,5-dicarboxylic acid） has been synthesized and structurally characterized by single-crystal diffraction. Compound 1 crystallizes in monoclinic, space group C2/c with a = 18.3928（8）, b = 8.3299（5）, c = 13.682（7） A, β = 113.179（2）°, V = 1926.9（10）A^3, Z = 8 and Dc = 2.784 g·cm^-3. In the solid state, this disilver（I） compound can aggregate to furnish the energetically stable ligand-unsupported Ag^I-Ag^I interaction concomitant with significant photoluminescence changes in different aggregate states, and such argentophilicity interaction is also supported by molecular orbital calculations.

Synthesis, Crystal Structure and Fluorescent Property of [Ag3（μ3-I）2（μ2-dppm）3]I·0.5THF·0.5 H2O

The crystal structure of the title complex, [Ag3(μ3-I)2(μ2-dppm)3]I?0.5THF?0.5H2O (dppm = bis(diphenylphino) methane and THF = tetrahydrofuran), has been determined by single- crystal X-ray diffraction, revealing it consists of a trinuclear [Ag3I2(dppm)3]+ cation with a tri- gonal bipyramidal [Ag3(μ3-I)2] cluster, a discrete iodine anion, one half THF and one half H2O solvent molecules. The short Ag???Ag distances (Ag(1)???Ag(2) = 3.1307(4), Ag(1)???Ag(3) = 3.2527(4) and Ag(2)???Ag(3) = 3.3209(4) ?) in the cluster suggest the existence of argentophilic interactions between the silver atoms. The crystal belongs to monoclinic, space group P21/n with a = 19.172(2), b = 18.819(1), c = 21.316(1) ?, β = 91.081(4)°, V = 7689.4(9) ?3, Dc = 1.643 g/cm3, Z = 4, C77H71Ag3I3OP6, Mr = 1902.47, μ = 2.127 mm-1, λ(MoKα) = 0.71073 ? and F(000) = 3724. The final R = 0.0584 and wR = 0.0928 for 8470 observed reflections with I > 2σ(I). The electronic emission spectrum shows a broad band around 408 nm which is assigned to the ligand-to-metal charge-transfer (LMCT) [I- → Ag3] excited state, mixed with a metal-centred (ds/dp) state.

Core engineering of paired core-shell silver nanoclusters

Unlike the facile modulation of surface structure through protecting ligands,the core shielded by outer shell of silver nanoclusters is still hard to be controlled.Ligand effects may seep into the incipient growth of silver core.However,the comparable cases to validate such hypothesis are currently lacking.Herein,we shed light on two core-shell silver nanoclusters,Ag_(7)S_(6)@Ag_(48)(SD/Ag55b,SD=SunDi)and Ag_(6)S_(6)@Ag_(48)(SD/Ag54b),differing in only one silver atom in the core which varies from a pentagon-bipyramidal Ag_(7)to an octahedral Ag_(6)while keeping the Ag_(48)shielding shell almost the same.Although no direct bonding between alkynes and silver core is observed in them,we propose that the ligand effect still exerts profound influences on the size and geometry of silver core.The solution behaviours and complete ligand-exchange reaction of SD/Ag55b in CH_(2)Cl_(2)are investigated using electrospray ionization mass spectrometry.Due to more and stronger argentophilic interactions,SD/Ag55b exhibits room-temperature phosphorescence with a 40 nm red-shift compared to that of SD/Ag54b in CH_(2)Cl_(2).This work not only presents effective fabrication of silver nanoclusters via synergism of dithiophosphate and alkyne ligands,but also provides us a pair of comparable examples to understand substitution group effect of protecting ligand on the core structures and properties.

Synthesis,Structure and Luminescence Properties of Dumbbell-like Silver Clusters

In this work,three stable dumbbell-shaped silver clusters 1~3,formed by a novel bifunctional ligand Ph2P-C6H4-3-C=CH,are presented.All three complexes have cage structures constructed with thirty-six silver atoms,which are templated by chloride anions.During the self-assembly process of silver acetylides,argentophilic interactions and Ag(I)-ethynide interactions are important for the formation of silver cores to yield a diversity of silver clusters.Weak molecular interactions(π-π,C-H…π,C-H…F,C-H…O)are also found in these complexes,which are crucial to stabilizing these silver clusters.Compared with simple alkynyl ligands(RC≡C-),the introduction of phosphine groups into alkynyl ligand can effectively control the undesired infinite growth of silver acetylides.The photophysical behaviors of complexes 1~3 are studied,showing intense orange roomtemperature luminescence in the solid state upon the exposure to UV light.The luminescence mainly arises from ligand-to-metal charge transfer(LMCT)and metal-cluster-centered transitions(MC)within the silver clusters.