A Comparison of Structure and Stability between the Group 11 Halide Tetramers M4X4 (M = Cu, Ag, or Au; X = F, Cl, Br, or I) and the Group 11 Chloride and Bromide Phosphanes (XMPH3)4

Structures and growth pathways of AunCln+3- (n ≤ 7) cluster anions

Gold chloride clusters play an important role in catalysis and materials chemistry. Due to the diversity of their species and isomers, there is still a dearth of structural studies at the molecular level. In this work, anions of AunCln+3 - and AunCln+5 - (n = 2-4) clusters were obtained by laser desorption/ionization mass spectrometry (LDI MS), and the most stable isomers of AunCln+3 - were determined after a thorough search and optimization at the TPSSh/aug-cc-pVTZ/ECP60MDF level. The results indicate that all isomers with the lowest energy have a planar zigzag skeleton. In each species, there is one Au(III) atom at the edge connected with four Cl atoms, which sets it from the other Au(I) atoms. Four growth pathways for AunCln+3 - (n = 2-7) clusters are proposed (labelled R1, R2, R3 and R4). They are all associated with an aurophilic contact and are exothermic. The binding energies tend to stabilize at ∼ -41 kcal/mol when the size of the cluster increases in all pathways. The pathway R1, which connects all the most stable isomers of the respective clusters, is characterized by cluster growth due to aurophilic interactions at the terminal atom of Au(I) in the zigzag chains. In the pathway of R4 involving Au-Au bonding in its initial structures (n ≤ 3), the distance between intermediate gold atoms grows with cluster size, ultimately resulting in the transfer of the intermediate Au-Au bonding into aurophilic interaction. The size effect on the structure and aurophilic interactions of these clusters will be better understood based on these discoveries, potentially providing new insights into the active but elusive chemical species involved in the corresponding catalytic reactions or nanoparticle synthesis processes.

Evaluation of Ligands Effect on the Photophysical Properties of Copper Iodide Clusters

Luminescent materials based on copper complexes are currently receiving increasing attention because of their rich photophysical properties, opening a wide field of applications. The copper iodide clusters formulated [Cu₄I₄L₄] (L = ligand), are particularly relevant for the development of multifunctional materials based on their luminescence stimuli-responsive properties. In this context, controlling and modulating their photophysical properties is crucial and this can only be achieved by thorough understanding of the origin of the optical properties. We thus report here, the comparative study of a series of cubane copper iodide clusters coordinated by different phosphine ligands, with the goal of analyzing the effect of the ligands nature on the photoluminescence properties. The synthesis, structural, and photophysical characterizations along with theoretical investigations of copper iodide clusters with ligands presenting different electronic properties, are described. A method to simplify the analysis of the ³¹P solid-state NMR spectra is also reported. While clusters with electron-donating groups present classical luminescence properties, the cluster bearing strong electron-withdrawing substituents exhibits original behavior demonstrating a clear influence of the ligands properties. In particular, the electron-withdrawing character induces a decrease in energy of the unoccupied molecular orbitals, that consequently impacts the emission properties. The modification of the luminescence thermochromic properties of the clusters are supported by density functional theory (DFT) calculations. This study demonstrates that the control of the luminescence properties of these compounds can be achieved through modification of the coordinated ligands, nevertheless the role of the crystal packing should not be underestimated.

Silver(i) complexes with 1'-(diphenylphosphino)-1-cyanoferrocene: the art of improvisation in coordination

1'-(Diphenylphosphino)-1-cyanoferrocene () reacts with silver(i) halides at a 1 : 1 metal-to-ligand ratio to afford the heterocubane complexes [Ag(μ3-X)(-κP)]4, where X = Cl (), Br (), and I (). In addition, the reaction with AgCl with 2 equiv. of leads to chloride-bridged dimer [(μ-Cl)2{Ag(-κP)2}2] () and, presumably, also to [(μ(P,N)-){AgCl(-κP)}]2 (). While similar reactions with AgCN furnished only the insoluble coordination polymer [(-κP)2Ag(NC)Ag(CN)]n (), those with AgSCN afforded the heterocubane [Ag(-κP)(μ-SCN-S,S,N)]4 () and the thiocyanato-bridged disilver(i) complex [Ag(-κP)2(μ-SCN-S,N)]2 (), thereby resembling reactions in the AgCl- system. Attempted reactions with AgF led to ill-defined products, among which [Ag(-κP)2(μ-HF2)]2 () and [(μ-SiF6){Ag(-κP)2}2] () could be identified. The latter compound was prepared also from Ag2[SiF6] and . Reactions between and AgClO4 or Ag[BF4] afforded disilver complexes [(μ(P,N)-)Ag(ClO4-κO)]2 () and [(μ(P,N)-)Ag(BF4-κF)]2 () featuring pseudolinear Ag(i) centers that are weakly coordinated by the counter anions. A similar reaction with Ag[SbF6] followed by crystallization from ethyl acetate produced an analogous complex, albeit with coordinated solvent, [(μ(P,N)-)Ag(AcOEt-κO)]2[SbF6]2 (). Ultimately, a compound devoid of any additional ligands at the Ag(i) centers, [(μ(P,N)-)Ag]2[B(C6H3(CF3)2-3,5)4]2 (), was obtained from the reaction of with silver(i) tetrakis[3,5-bis(trifluoromethyl)phenyl]borate. The reaction of Ag[BF4] with two equivalents of produced unique coordination polymer [Ag(-κP)(μ(P,N)-)]n[BF4]n (), the structure of which contained one of the phosphinoferrocene ligands coordinated as a P,N-chelate and the other forming a bridge to an adjacent Ag(i) center. All of these compounds were structurally characterized by single-crystal X-ray crystallography, revealing that the lengths of the bonds between silver and its anionic ligand(s) typically exceed the sum of the respective covalent radii, which is in line with the results of theoretical calculations at the density-functional theory (DFT) level, suggesting that standard covalent dative bonds are formed between silver and phosphorus (soft acid/soft base interactions) while the interactions between silver and the ligand's nitrile group (if coordinated) or the supporting anion are of predominantly electrostatic nature.

Dissociative iodomethane adsorption on Ag-MOR and the formation of AgI clusters: an ab initio molecular dynamics study

Using ab initio MD simulations, a full transformation path of iodomethane in Ag-MOR is explored: from adsorption to formation of AgI clusters.

Coinage metal coordination chemistry of stable primary, secondary and tertiary ferrocenylethyl-based phosphines

Ferrocene-based phosphines constitute an important auxiliary ligand in inorganic chemistry. Utilizing the (ferrocenylethyl)phosphines (FcCH2CH2)3-nHnP (Fc = ferrocenyl; n = 2, 1; n = 1, 2; n = 0, 3) the synthesis of a series of coordination complexes [(FcCH2CH2)3-nHnPCuCl]4 (n = 2, 1-CuCl; n = 0, 3-CuCl), [(FcCH2CH2)2HPCuCl] (2-CuCl), {[(FcCH2CH2)H2P]2AgCl}2 (1-AgCl), [(FcCH2CH2)2HPAgCl] (2-AgCl), [(FcCH2CH2)3PAgCl]4 (3-AgCl), [(FcCH2CH2)3PM(OAc)]4 (M = Cu, 3-CuOAc M = Ag, 3-AgOAc), [(FcCH2CH2)3-nHnPAuCl] (n = 1, 2-AuCl; n = 0, 3-AuCl), via the reaction between the free phosphine and MX (M = Cu, Ag and Au; X = Cl, OAc), is described. The reaction between the respective phosphine with a suspension of metal-chloride or -acetate in a 1 : 1 ratio in THF at ambient temperature affords coordinated phosphine-coinage metal complexes. Varying structural motifs are observed in the solid state, as determined via single crystal X-ray analysis of 1-CuCl, 3-CuCl, 1-AgCl, 3-AgCl, 3-CuOAc, 3-AgOAc, 2-AuCl and 3-AuCl. Complexes 1-CuCl and 3-CuCl are tetrameric Cu(i) cubane-like structures with a Cu4Cl4 core, whereas silver complexes with primary and tertiary phosphine reveal two different structural types. The structure of 1-AgCl, unlike the rest, displays the coordination of two phosphines to each silver atom and shows a quadrangle defined by two Ag and two Cl atoms. In contrast, 3-AgCl is distorted from a cubane structure via elongation of one of the ClAg distances. 3-CuOAc and 3-AgOAc are isostructural with step-like cores, while complexes 2-AuCl and 3-AuCl reveal a linear geometry of a phosphine gold(i) chloride devoid of any aurophilic interactions. All of the complexes were characterized in solution by multinuclear (1)H, (13)C{(1)H} and (31)P NMR spectroscopic techniques; the redox chemistry of the series of complexes was examined using cyclic voltammetry. This class of complexes has been found to exhibit one reversible Fe(ii)/Fe(iii) oxidation couple, suggesting the absence of electronic communication between the ferrocenyl units on individual phosphine ligands as well as between different phosphines on the polymetallic cores.

First principles study on the structural evolution and properties of (MCl)n (n = 1–12, M = Cu, Ag) clusters

Energetic gaps (E − E_fit) and second differences of binding energies (Δ₂E) for (CuCl)_n and (AgCl)_n clusters as a function of cluster size, n.

Subtle Modulation of Cu4X4L2 Phosphine Cluster Cores Leads to Changes in Luminescence

A series of Cu4X4(PPh2py)2 compounds (X = Cl (1), Br (2), I (3), PPh2py = 2-(diphenylphosphino)pyridine) were prepared and characterized using X-ray crystallography, NMR, UV-vis, and luminescence spectroscopy. The copper chloride and bromide clusters have Cu4X4 octahedral cores while the copper iodide clusters contain an unprecedented butterfly shaped core. Crystallization of the copper bromide and iodide clusters from the appropriate solvent produced the solvates 2·2CH2Cl2, 2·2CHCl3, and 3·0.5CH2Cl2 where the presence of the lattice solvate influences the overall structural properties. Using TD-DFT calculations, the emission was assigned to a mixed metal- and halide-to-ligand charge transfer, (M + X)LCT. Subtle differences in the copper core geometry and μ-halide bonding perturb the emissions of these copper(I) halide clusters.

Dimeric 1:2 adduct of β,β′-bis(diphenylphosphino)porphyrin with silver(I) chloride

A 2,18-bis(diphenylphosphino)porphyrin ligand undergoes complexation with silver(I) chloride to afford a stable phosphine-silver complex. X-ray crystallographic analysis of the complex revealed a dimeric structure of a 1:2 adduct of the diphosphine and silver(I) chloride, where each phosphorus atom coordinates a silver atom. The four AgCl units construct a distorted cubic cluster with small metallophilic interaction. Variable temperature 31 P NMR study exhibited a slow ligand exchange process between 107 Ag and 109 Ag at high temperature.

Predicting crystal structures and properties of matter under extreme conditions via quantum mechanics: the pressure is on

The role of quantum mechanical calculations in understanding and predicting the behavior of matter at extreme pressures is discussed in this feature contribution.

Tetra-μ3-iodido-tetra-kis-[(tri-n-butyl-phosphane-κP)copper(I)]

The title complex, [Cu₄I₄(C₁₂H₂₇P)₄], crystallizes with six mol­ecules in the unit cell and with three independent one-third mol­ecule fragments, completed by application of the relevant symmetry operators, in the asymmetric unit. The tetranuclear copper core shows a tetrahedral geometry (site symmetry 3..). The I atoms also form a tetra­hedron, with I⋯I distances of 4.471 (1) Å. Both tetra­hedra show an orientation similar to that of a pair of self-dual platonic bodies. The edges of the I-tetra­hedral structure are capped to the face centers of the Cu-tetra­hedron and vice versa. The Cu_face⋯I distances are 2.18 Å (averaged) and the I_face⋯Cu distances are 0.78 Å (averaged). As a geometric consequence of these properties there are eight distorted trigonal–bipyramidal polyhedra evident, wherein each trigonal face builds up the equatorial site and the opposite Cu⋯I positions form the axial site. As expected, the n-butyl moieties are highly flexible, resulting in large elongations of their anisotropic displacement parameters. Some C atoms of the n-butyl groups were needed to fix alternative discrete disordered positions.

Molecular and electronic structure, magnetotropicity and absorption spectra of benzene-trinuclear copper(I) and silver(I) trihalide columnar binary stacks

The molecular and electronic structures, stabilities, bonding features, magnetotropicity and absorption spectra of benzene-trinuclear Cu(I) and Ag(I) trihalide columnar binary stacks with the general formula [c-M(3)(μ(2)-X)(3)](n)(C(6)H(6))(m) (M = Cu, Ag; X = halide; n, m ≤ 2) have been investigated by means of electronic structure calculation methods. The interaction of c-M(3)(μ(2)-X)(3) clusters with one and two benzene molecules yields 1:1 and 1:2 binary stacks, while benzene sandwiched 2:1 stacks are formed upon interaction of two c-M(3)(μ(2)-X)(3) clusters with one benzene molecule. In all binary stacks the plane of the alternating c-M(3)(μ(2)-X)(3) and benzene components adopts an almost parallel orientation. The separation distance between the centroids of the benzene and the proximal c-M(3)(μ(2)-X)(3) metallic cluster found in the range 2.97-3.33 Å at the B97D/Def2-TZVP level is indicative of a π···π stacking interaction mode, for the centroid separation distance is very close to the sum of the van der Waals radii of Cu···C (3.10 Å) and Ag···C (3.44 Å). Energy decomposition analysis (EDA) at the SSB-D/TZP level revealed that the dominant term in the c-M(3)(μ(2)-X)(3)···C(6)H(6) interaction arises from dispersion and electrostatic forces while the covalent interactions are predicted to be negligible. On the other hand, charge decomposition analysis (CDA) illustrated very small charge transfer from C(6)H(6) toward the c-M(3)(μ(2)-X)(3) clusters, thus reflecting weak π-base/π-acid interactions which are further corroborated by the respective electrostatic potentials and the fact that the total dipole moment vector points to the center of the metallic ring of the c-M(3)(μ(2)-X)(3) cluster. The absorption spectra of all aromatic columnar binary stacks simulated by means of TD-DFT calculations showed strong absorptions in the UV region. The main features of the simulated absorption spectra are thoroughly analyzed, and assignments of the contributing electronic transitions are given. The magnetotropicity of the binary stacks evaluated by the NICS(zz)-scan curves indicated an enhancement of the diatropicity of the inorganic ring upon interaction with the aromatic benzene molecule. Noteworthy is the slight enhancement of the diatropicity of the benzene ring, particularly in the region between the interacting rings, probably due to the superposition (coupling) of the diamagnetic ring currents of the interacting aromatic ring systems.

Structural effects in molecular metal halides

Metal halides are a relatively large class of inorganic compounds that participate in many industrial processes, from halogen metallurgy to the production of semiconductors. Because most metal halides are ionic crystals at ambient conditions, the term "molecular metal halides" usually refers to vapor-phase species. These gas-phase molecules have a special place in basic research because they exhibit the widest range of chemical bonding from the purely ionic to mostly covalent bonding through to weakly interacting systems. Although our focus is basic research, knowledge of the structural and thermodynamic properties of gas-phase metal halides is also important in industrial processes. In this Account, we review our most recent work on metal halide molecular structures. Our studies are based on electron diffraction and vibrational spectroscopy, and increasingly, we have augmented our experimental work with quantum chemical computations. Using both experimental and computational techniques has enabled us to determine intriguing structural effects with better accuracy than using either technique alone. We loosely group our discussion based on structural effects including "floppiness", relativistic effects, vibronic interactions, and finally, undiscovered molecules with computational thermodynamic stability. Floppiness, or serious "nonrigidity", is a typical characteristic of metal halides and makes their study challenging for both experimentalists and theoreticians. Relativistic effects are mostly responsible for the unique structure of gold and mercury halides. These molecules have shorter-than-expected bonds and often have unusual geometrical configurations. The gold monohalide and mercury dihalide dimers and the molecular-type crystal structure of HgCl(2) are examples. We also examined spin-orbit coupling and the possible effect of the 4f electrons on the structure of lanthanide trihalides. Unexpectedly, we found that the geometry of their dimers depends on the f electron configuration. Metal halides are unique in exhibiting strong vibronic interactions such as the Jahn-Teller effect and the related Renner-Teller effect. Some metal trihalide molecules have an almost T-shape due to static Jahn-Teller distortions. The nonlinear structure with a 150 degree bond angle of the chromium dichloride molecule demonstrates the Renner-Teller effect. Finally, we present a few examples of unknown structures that appear to be thermodynamically stable, including gold and silver triiodides and all silver subhalides. The combination of experimental and computational techniques has brought new insights to the structural chemistry of metal halides. We expect that the continuing progress in computational chemistry will shed further light on the intricate details of these and other molecular structures.

Luminescent Amidate-Bridged One-Dimensional Platinum(II)−Thallium(I) Coordination Polymers Assembled via Metallophilic Attraction

The neutral square-planar complexes [Pt(RNH2)2(NHCO(t)Bu)2] (R = H, 1; Et, 2) and [Pt(DACH)(NHCO(t)Bu)2] (DACH = 1,2-diaminocyclohexane, 3) act as metalloligands and make bonds to closed-shell Tl(I) ions to afford one- and two-dimensional platinum-thallium oligomers or polymers based on heterobimetallic backbones. A series of heteronuclear platinum(II)-thallium(I) complexes have been synthesized and structurally characterized. The structures of the Pt-Tl compounds resulted from [Pt(RNH2)2(NHCO(t)Bu)2] and TlX [X = NO3(-), ClO4(-), PF6(-), and Cp2Fe(CO2)2(2-)] are dependent on both counteranions and the amine substituents. The compounds [Pt(NH3)2(NHCO(t)Bu)2Tl]X (X = NO3(-), 8; ClO4(-), 9) adopt one-dimensional zigzag chain structures consisting of repeatedly stacked [Pt(NH3)2(NHCO(t)Bu)2Tl]+ units, whereas [{Pt(NH3)2(NHCO(t)Bu)2}2Tl2]X2 (X = PF6(-), 10) consists of a helical chain. Compound 3 reacts with Tl+ to give [{Pt(DACH)(NHCO(t)Bu)2}2Tl](NO3) x [Pt(DACH)(NHCO(t)Bu)2] x 3 H2O (14) and one-dimensional polymeric [{Pt(DACH)(NHCO(t)Bu)2}2Tl2]X2 (X = ClO4(-), 15; PF6(-), 16). Reactions of [Pt(DACH)(NHCOCH3)2] with Tl+ ions afford one-dimensional coordination polymers [{Pt(DACH)(NHCOCH3)2}2Tl2]X2 (X = NO3(-), 17; ClO4(-), 18; PF6(-), 19). The polymeric [{Pt(DACH)(NHCOR')2}2Tl2]2+ (R = CH3, (t)Bu) complexes adopt helical structures, which are generated around the crystallographic 2(1) screw axis. The distance between the coils corresponds to the unit cell length, which ranges from 22.58 to 22.68 A. The platinum-thallium bond distances fall in a narrow range around 3.0 A. The complexes derived from [Pt(NH3)2(NHCO(t)Bu)2] are luminescent at 77 K. The trinuclear complexes [{Pt(RNH2)(NHCO(t)Bu)2}2Tl]+ do not emit at room temperature but are emissive at 77 K, whereas the polymeric platinum-thallium complexes containing 1,2-diaminocyclohexane are intensively luminescent at both room temperature and 77 K. The color variations are interesting; 15 exhibits intense yellow-green, 16 exhibits green, and 17-19 exhibit blue luminescence. The presence of bonding between platinum and thallium is supported by the short metal-metal separations and the strong low-energy luminescence of these compounds in their solid states.

Copper Cation Interactions with Biologically Essential Types of Ligands: A Computational DFT Study

This work presents a systematic theoretical study on Cu(I) and Cu(II) cations in variable hydrogen sulfide-aqua-ammine ligand fields. These ligands model the biologically most common environment for Cu ions. Molecular structures of the complexes were optimized at the density functional theory (DFT) level. Subsequent thorough energy analyses revealed the following trends: (i) The ammine complexes are the most stable, followed by those containing the aqua and hydrogen sulfide ligands, which are characterized by similar stabilization energies. (ii) The most preferred Cu(I) coordination number is 2 in ammine or aqua ligand fields. A qualitatively different binding picture was obtained for complexes with H(2)S ligands where the 4-coordination is favored. (iii) The 4- and 5-coordinated structures belong to the most stable complexes for Cu(II), regardless of the ligand types. Vertical and adiabatic ionization potentials of Cu(I) complexes were calculated. Charge distribution (using the natural population analysis (NPA) method) and molecular orbital analyses were performed to elucidate the nature of bonding in the examined systems. The results provide in-depth insight into the Cu-binding properties and can be, among others, used for the calibration of bioinorganic force fields.

Structure and Bonding in Silver Halides. A Quantum Chemical Study of the Monomers: Ag2X, AgX, AgX2, and AgX3 (X = F, Cl, Br, I)

The molecular structure of all silver halide monomers, Ag(2)X, AgX, AgX(2), and AgX(3), (X = F, Cl, Br, I), have been calculated at the B3LYP, MP2, and CCSD(T) levels of theory by using quasirelativistic pseudopotentials for all atoms except fluorine and chlorine. All silver monohalides are stable molecules, while the relative stabilities of the subhalides, dihalides, and trihalides considerably decrease toward the larger halogens. The ground-state structure of all Ag(2)X silver subhalides has C(2)(v)() symmetry, and the molecules can be best described as [Ag(2)](+)X(-). Silver dihalides are linear molecules; AgF(2) has a (2)Sigma(g) ground state, while all of the other silver dihalides have a ground state of (2)Pi(g) symmetry. The potential energy surface (PES) of all silver trihalides has been investigated. Neither of these molecules has a D(3)(h)() symmetric trigonal planar geometry, due to their Jahn-Teller distortion. The minimum energy structure of AgF(3) is a T-shaped structure with C(2)(v)() symmetry. For AgCl(3), AgBr(3), and AgI(3), the global minimum is an L-shaped structure, which lies outside the Jahn-Teller PES. This structure can be considered as a donor-acceptor system, with X(2) acting as donor and AgX as acceptor. Thus, except for AgF(3), in the other three silver trihalides, silver is not present in the formal oxidation state 3.

Solid State Density Functional Calculations for the Group 11 Monohalides

The group 11 monohalides are characterized by a variety of different solid-state structures and modifications. The copper halides crystallize mainly in a cubic zinc blende structure, while silver halides are mostly found in a rock salt modification. Completely different are the gold compounds where relativistic effects change the symmetry from a cubic to a chainlike AuX arrangement (X = F, Cl, Br, I) with short Au-Au internuclear distances. Here we present a systematic study of all solid state group 11 halides by scalar relativistic density functional theory for the experimentally known and observed structures, as well as for other unknown modifications and compare their relative stability.