Photoluminescence of 1-D Copper(I) Cyanide Chains: A Theoretical Description

An Insight into nd10 Metal Cyanide-based Coordination Polymers Through ab-initio Calculations: Electronic Properties and Optical Response

Semiconductors are essential for modern life since they are the basis of many current technologies that are related to better living standards. Some of them, characterized by the periodic assembling of metal cyanides with filled d-shell (nd¹⁰ ) constitute an interesting series of cyanide-based coordination polymers with physical properties such like anomalous anisotropic thermal expansion and quantum confinement effects related to the polymer's width that can be exploited for technological applications. Herein, the electronic structure of nd¹⁰ metal cyanide-based systems were studied both experimentally and through Density Functional Theory. The band gap found for one-dimensional (1D) -M-C≡N- (M=Cu, Ag, Au) and tetrahedral M-(C≡N)₂ (M=Zn, Cd, Hg) systems can be attributed to Laporte-allowed π → ${\to }$ π* (Metal to Ligand Charge Transfer mechanism) combined with metal center (d → ${\to }$ s,p) electronic transitions. Aurophilic bonding was found on the AuCN structure, and a new forbidden electronic transition associated to its band gap is reported. Computed effective and reduced masses from carriers revealed that carrier mobility and quantum confinement effects are greater in 1D systems.

A novel three-dimensional copper(I) cyanide coordination polymer constructed from various bridging ligands: synthesis, crystal structure and characterization

The cyanide ligand can act as a strong σ-donor and an effective π-electron acceptor that exhibits versatile bridging abilities, such as terminal, μ₂-C:N, μ₃-C:C:N and μ₄-C:C:N:N modes. These ligands play a key role in the formation of various copper(I) cyanide systems, including one-dimensional (1D) chains, two-dimensional (2D) layers and three-dimensional (3D) frameworks. According to the literature, numerous coordination polymers based on terminal, μ₂-C:N and μ₃-C,C,N bridging modes have been documented so far. However, systems based on the μ₄-C:C:N:N bridging mode are relatively rare. In this work, a novel cyanide-bridged 3D Cu^I coordination framework, namely poly[(μ₂-2,2'-biimidazole-κ²N³:N^3')(μ₄-cyanido-κ⁴C:C:N:N)(μ₂-cyanido-κ²C:N)dicopper(I)], [Cu₂(CN)₂(C₆H₆N₄)]_n, (I), was synthesized hydrothermally by reaction of environmentally friendly K₃[Fe(CN)₆], CuCl₂·2H₂O and 2,2'-biimidazole (H₂biim). It should be noted that cyanide ligands may act as reducing agents to reduce Cu^II to Cu^I under hydrothermal conditions. Compound (I) contains diverse types of bridging ligands, such as μ₄-C:C:N:N-cyanide, μ₂-C:N-cyanide and μ₂-biimidazole. Interestingly, the [Cu₂] dimers are bridged by rare μ₄-C:C:N:N-mode cyanide ligands giving rise to the first example of a 1D dimeric {[Cu₂(μ₄-C:C:N:N)]ⁿ⁺}_n infinite chain. Furthermore, adjacent dimer-based chains are linked by μ₂-C:N bridging cyanide ligands, generating a neutral 2D wave-like (4,4) layer structure. Finally, the 2D layers are joined together via bidentate bridging H₂biim to create a 3D cuprous cyanide network. This arrangement leads to a systematic variation in dimensionality from 1D chain→2D sheet→3D framework by different types of bridging ligands. Compound (I) was further characterized by thermal analysis, solid-state UV-Vis diffuse-reflectance and photoluminescence studies. The solid-state UV-Vis diffuse-reflectance spectra show that compound (I) is a wide-gap semiconductor with band gaps of 3.18 eV. The photoluminescence study shows a strong blue-green photoluminescence at room temperature, which may be associated with metal-to-ligand charge transfer.

Synthesis and Luminescence of Optical Memory Active Tetramethylammonium Cyanocuprate(I) 3D Networks

The structures of three tetramethylammonium cyanocuprate(I) 3D networks [NMe₄]₂[Cu(CN)₂]₂•0.25H₂O (1), [NMe₄][Cu₃(CN)₄] (2), and [NMe₄][Cu₂(CN)₃] (3), (Me₄N = tetramethylammonium), and the photophysics of 1 and 2 are reported. These complexes are prepared by combining aqueous solutions of the simple salts tetramethylammonium chloride and potassium dicyanocuprate. Single-crystal X-ray diffraction analysis of complex 1 reveals {Cu₂(CN)₂(μ₂-CN)₄} rhomboids crosslinked by cyano ligands and D_3h {Cu(CN)₃} metal clusters into a 3D coordination polymer, while 2 features independent 2D layers of fused hexagonal {Cu₈(CN)₈} rings where two Cu(I) centers reside in a linear C_∞v coordination sphere. Metallophilic interactions are observed in 1 as close Cu⋯Cu distances, but are noticeably absent in 2. Complex 3 is a simple honeycomb sheet composed of trigonal planar Cu(I) centers with no Cu^…Cu interactions. Temperature and time-dependent luminescence of 1 and 2 have been performed between 298 K and 78 K and demonstrate that 1 is a dual singlet/triplet emitter at low temperatures while 2 is a triplet-only emitter. DFT and TD-DFT calculations were used to help interpret the experimental findings. Optical memory experiments show that 1 and 2 are both optical memory active. These complexes undergo a reduction of emission intensity upon laser irradiation at 255 nm although this loss is much faster in 2. The loss of emission intensity is reversible in both cases by applying heat to the sample. We propose a light-induced electron transfer mechanism for the optical memory behavior observed.

Two copper(i) cyanide coordination polymers modified by semi-rigid bis(benzimidazole) ligands: syntheses, crystal structures, and electrochemical and photocatalytic properties

Two Cu(i) cyanide complexes with semi-rigid bis(benzimidazole) ligands were synthesized and characterized. Both complexes manifest photocatalytic activities for the degradation of methylene blue.

Electronic, bonding, and optical properties of 1d [CuCN]n (n = 1-10) chains, 2d [CuCN]n (n = 2-10) nanorings, and 3d [Cun (CN)n ]m (n = 4, m = 2, 3; n = 10, m = 2) tubes studied by DFT/TD-DFT methods

The electronic, bonding, and photophysical properties of one-dimensional [CuCN](n) (n = 1-10) chains, 2-D [CuCN](n) (n = 2-10) nanorings, and 3-D [Cu(n)(CN)(n)](m) (n = 4, m = 2, 3; n = 10, m = 2) tubes are investigated by means of a multitude of computational methodologies using density functional theory (DFT) and time-dependent-density-functional theory (TD-DFT) methods. The calculations revealed that the 2-D [CuCN](n) (n = 2-10) nanorings are more stable than the respective 1-D [CuCN](n) (n = 2-10) linear chains. The 2-D [CuCN](n) (n = 2-10) nanorings are predicted to form 3-D [Cun (CN)(n)](m) (n = 4, m = 2, 3; n = 10, m = 2) tubes supported by weak stacking interactions, which are clearly visualized as broad regions in real space by the 3D plots of the reduced density gradient. The bonding mechanism in the 1-D [CuCN](n) (n = 1-10) chains, 2-D [CuCN](n) (n = 2-10) nanorings, and 3-D [Cu(n)(CN)(n)](m) (n = 4, m = 2, 3; n = 10, m = 2) tubes are easily recognized by a multitude of electronic structure calculation approaches. Particular emphasis was given on the photophysical properties (absorption and emission spectra) of the [CuCN](n) chains, nanorings, and tubes which were simulated by TD-DFT calculations. The absorption and emission bands in the simulated TD-DFT absorption and emission spectra have thoroughly been analyzed and assignments of the contributing principal electronic transitions associated to individual excitations have been made.

Two novel topological structures of [Cu(CN)] coordination polymers modified by flexible triazole ligands

Triazole ligands have been introduced into the {Cu(CN)} skeleton to produce appealing polymers, which exhibit certain thermal stability and fluorescence properties.

Theoretical insights into the effect of amine and phosphine decoration on the photoluminescence of copper(i) and silver(i) coordination polymers

Ligand decoration shifts the excitation and emission spectra of coinage metal cyanides. DFT and TD-DFT calculations are used to identify the MOs involved the transitions that contribute to photoluminescence.

A cyano-bridged copper(ii)–copper(i) mixed-valence coordination polymer as a source of copper oxide nanoparticles with catalytic activity in C–N, C–O and C–S cross-coupling reactions

A cyano-bridged Cu(ii)–Cu(i) complex was synthesized and transformed into CuO nanoparticles. Their catalytic activity in C–N, C–O, and C–S cross-coupling reactions was explored.

Structure and applications of metal-organic framework based on cyanide and 3,5-dichloropyridine

The reaction of the aqueous/acetonitrile solutions of K3[Cu(CN)4] and 3,5-dichloropyridine (3,5-dClpy), in the presence of Me3SnCl affords a new metal-organic framework (MOF), (3)∞[(CuCN)2·(3,5-dClpy)2], 1. The structure of the MOF 1 was characterized by IR, UV-visible, TGA and X-ray single crystal analysis. The structure of MOF 1 consists of CuCN building blocks which are connected by CN group forming 1D-zig-zag chains. Each chain is bridged to another chain by hydrogen bonding organizing 2D-sheets. The structure of 1 is further close packed by hydrogen bonds, π-π stacking and lp-π interactions creating 3D-network. The emission spectra and the thermodynamic parameters from TGA of the MOF 1 were discussed. The MOF 1 was used as heterogeneous catalyst for the oxidative discoloration of methylene blue dye (MB) by dilute solution of hydrogen peroxide as oxidant. The in vitro cytotoxic activity has been evaluated against the human breast cancer cell lines MCF-7. The cytotoxic effect of the MOF 1 on the viability of MCF-7 cells was determined by MTT assay.

Radical-involved photosynthesis of AuCN oligomers from Au nanoparticles and acetonitrile

We show here the first radical route for the direct photosynthesis of AuCN oligomers with different sizes and shapes, as evidenced by TEM observations, from an Au nanoparticle/benzaldehyde/CH(3)CN ternary system in air under UV-light irradiation. This photochemical route is green, mild, and universal, which makes itself distinguishable from the common cyanidation process. Several elementary reaction steps, including the strong C-C bond dissociation of CH(3)CN and subsequent •CN radical addition to Au, have been suggested to be critical in the formation of AuCN oligomers based on the identification of •CN radical by in situ EPR and the radical trapping technique, and other reaction products by GC-MS and (1)H NMR, and DFT calculations. The resulting solid-state AuCN oligomers exhibit unique spectroscopic characters that may be a result of the shorter Au-Au distances (namely, aurophilicity) and/or special polymer-like structures as compared with gold cyanide derivatives in the aqueous phase. The nanosized AuCN oligomers supported on mesoporous silica showed relatively good catalytic activity on the homogeneous annulation of salicylaldehyde with phenylacetylene to afford isoflavanones employing PBu(3) as the cocatalyst under moderate conditions, which also serves as evidence for the successful production of AuCN oligomers.