Temperature-assisted formation of reversible metallophilic Au-Ag interaction arrays

A temperature-controlled self-assembly process in a solution of [Ag(terpy)] n n+ and [Au(C 6 F 5 ) 2 ] - units has been performed. For this, the crystallisation of the complex [{Au(C 6 F 5 ) 2 }Ag(terpy)] n under the same experimental conditions, changing only the temperature, allows the synthesis of polymorphs [{Au(C 6 F 5 ) 2 } 2 Ag 2 (terpy) 2 ] n (2a) at 298 K and [{Au(C 6 F 5 ) 2 }Ag(terpy)] n (2b) at 280 K. The X-ray diffraction studies previously reported for 2a revealed a polymeric structure with an unusual + + - - + + - - charge sequence, whereas for polymorph 2b, a more classical + - + - disposition has been obtained. The conversion of one polymorph into the other can be achieved by simple dissolution of one of them and by recrystallisation at the corresponding temperature. The mechanism of the formation of each polymorph is proposed in view of their 1 H NMR, 1 H-PGSE NMR and molar conductivity measurements

Role of dispersion interactions in Endohedral TM@(ZnS)12 structures

Role of dispersion interactions in Endohedral TM@(ZnS)(12) structures[EN] II−VI semiconducting materials are gaining attention due to their optoelectronic properties. Moreover, the addition of transition metals, TMs, might give them magnetic properties. The location and distance of the TM are crucial in determining such magnetic properties. In this work, we focus on small hollow (ZnS)12 nanoclusters doped with TMs. Because (ZnS)12 is a cage-like spheroid, the cavity inside the structure allows for the design of endohedral compounds resembling those of C60. Previous studies theoretically predicted that the first-row TM(ZnS)12 endohedral compounds were thermodynamically unstable compared to the surface compounds, where the TM atom is located at the surface of the cluster. The transition states connecting both structure families were calculated, and the estimated lifetimes of these compounds were predicted to be markedly small. However, in such works dispersion effects were not taken into account. Here, in order to check for the influence of dispersion on the possible stabilization of the desired TM(ZnS)12 endohedrally doped clusters, several functionals are tested and compare to MP2. It is found that the dispersion effects play a very important role in determining the location of the metals, especially in those TMs with the 4s3d shell half-filled or completely filled. In addition, a complete family of TM doped (ZnS)12 nanoclusters is explored using ab initio molecular dynamics simulations and local minima optimizations that could guide the experimental synthesis of such compounds. From the magnetic point of view, the Cr(7S)@(ZnS)12 compound is the most interesting case, since the endohedral isomer is predicted to be the global minimum. Moreover, molecular dynamics simulations show that when the Cr atom is located at the surface of the cluster, it spontaneously migrates toward the center of the cavity at room temperature.Financial support comes from Eusko Jaurlaritza through project IT1254-19. The authors are thankful for technical and human support provided by SGIker (UPV/EHU, ERDF, EU). E.J.I. acknowledges the support of the Ikerbasque Fellowship. E.R.C. acknowledges funding from the Juan de la Cierva program IJCI-2017-34658

El ciudadano José López Rubio á D. José Ruiz de Luzuriaga

A Mont. 09/2/40(44

Polarized supramolecular aggregates based on luminescent perhalogenated gold derivatives

Reaction of [Au(C6F5)(tht)] (tht = tetrahydrothiophene) with 1,3,5-triaza-7-phosphaadamantane (PTA) and 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]-nonane (DAPTA) leads to the formation of [Au(C6F5)(phosph)] (phosph = PTA, 1; phosph = DAPTA, 2). The compounds are slightly soluble in water and aggregate at higher concentrations giving rise to the formation of needle- and rod-like structures (1) and well-organized spherical aggregates (2). Compounds 1 and 2 were reacted with AgPF6 giving rise to the formation in all cases of luminescent water soluble 1:1 Au·Ag heterometallic complexes, as evidenced by X-ray crystal structure determination. The use of different silver salts that differ on the counterion induces changes on the resulting luminescence and aggregation morphology

1,4-Bis(2′-pyridylethynyl)benzene as a ligand in heteronuclear gold–thallium complexes. Influence of the ancillary ligands on their optical properties

The reaction of 1,4-bis(2′-pyridylethynyl)benzene (L) with [{Au(C6X5)2}Tl]n affords new heterometallic AuI/TlI complexes with different stoichiometries, structural arrangements and optical properties depending on the halogens present in the aryl group. The chlorinated derivative [{Au(C6Cl5)2}Tl(L)]n (1) displays polymeric chains built thanks to unsupported Au⋯Tl interactions and bridging bidentate ligands between adjacent chains, while in the fluorinated species [{Au(C6F5)2}2Tl2(L)2]n (2), also containing N-donor bridging ligands and Au⋯Tl contacts, polymerization occurs via Tl⋯Caryl non-bonding interactions between neighbouring molecules. The optical properties of 1 and 2 have been studied experimentally and theoretically, concluding that the luminescence of 1 in the solid state has its origin in the Au⋯Tl interactions, and that the Tl⋯Caryl interactions in 2 favour a non-radiative deactivation pathway that avoids luminescence. The strength of the non-bonding interactions present in 1 has also been theoretically studied at the HF and MP2 levels, revealing the metallophilic contact as the strongest one.This work was supported by the D.G.I. (MEC)/FEDER (CTQ2013-48635-C2-2-P).Peer reviewe

Mononuclear and pentanuclear Zn(II) complexes with hydrazonyl-thiazoles: structural and photophisical study

Јефтина, нискотоксична координациона једињења Zn(II) представљају обећавајуће кандидате за различите примене, укључујући фотолуминесцентне материјале. У овом раду су представљена два комплекса Zn(II) са хидразонил-тиазолским лигандима на бази пиридина (HLS1 и HLS2), који су синтетсани директном реакцијом лиганaда и Zn(CH3COO)2∙2H2O. Пентануклеарни комплекс [Zn5(HLS1)4(CH3COO)6] (1-AcO; Слика 1) кристалише у моноклиничној P21/n просторној групи са половином молекула по асиметричној јединици, при чему се централни јон Zn(II) налази на центру инверзије (Викофово слово c). Мононуклеарни комплекс [Zn(HLS2)(CH3COO)(H2O)] (2-AcO; Слика 2) кристалише у триклиничној P¬–1 просторној групи са једним молекулом по асиметричној јединици. Експеримент дифракције X-зрака са узорка праха je потврдио да су добијени једнофазни производи. Урађена је детаљна анализа типова и енергетске дистрибуције интермолекулских интеракција. Симетричан комплекс 1-AcO није фотолуминесцентан, за разлику од комплекса 2-AcO. Квантно-механички прорачуни теорије функционала густине (DFT) и временски зависне теорије функционала густине (TD-DFT) су расветлили порекло фотолуминесцентних својстава комплекса 2-AcO.Inexpensive, low-toxic Zn(II) coordination compounds are represent promising candidates for various applications, including photoluminescent materials. In this study we report two zinc(II) complexes with thiazolyl-hydrazone-based ligands (HLS1 and HLS2), which were synthesized by direct reaction of the ligands with Zn(CH3COO)2∙2H2O. Pentanuclear complex [Zn5(HLS1)4(CH3COO)6] (1-AcO; Figure 1) crystalizes in monoclinic P21/n space group with half of the molecule in the asymmetric unit, where Zn3 atoms lie at inversion center (Wyckoff letter c). Mononuclear [Zn(HLS2)(CH3COO)(H2O)] (2-AcO; Figure 2) crystalizes in triclinic P‒1 space group with one molecule in the asymmetric unit (Figure 2). Powder X-ray diffraction experiments confirmed that single-phase products were obtained. A detailed analysis of types and energy distribution of intermolecular interactions was performed. The symmetrical 1-AcO does not exhibit photophysical properties, unlike asymmetrical 2-AcO. Quantum-mechanical calculations of density functional theory (DFT) and time-dependent DFT provided insight into origin of the photoluminescent properties of 2-AcO

Synthesis, Photochemical, and Redox Properties of Gold(I) and Gold(III) Pincer Complexes Incorporating a 2,2′:6′,2″-Terpyridine Ligand Framework

Reaction of [Au(C6F5)(tht)] (tht = tetrahydrothiophene) with 2,2′:6′,2″-terpyridine (terpy) leads to complex [Au(C6F5)(η1-terpy)] (1). The chemical oxidation of complex (1) with 2 equiv of [N(C6H4Br-4)3](PF6) or using electrosynthetic techniques affords the Au(III) complex [Au(C6F5)(η3-terpy)](PF6)2 (2). The X-ray diffraction study of complex 2 reveals that the terpyridine acts as tridentate chelate ligand, which leads to a slightly distorted square-planar geometry. Complex 1 displays fluorescence in the solid state at 77 K due to a metal (gold) to ligand (terpy) charge transfer transition, whereas complex 2 displays fluorescence in acetonitrile due to excimer or exciplex formation. Time-dependent density functional theory calculations match the experimental absorption spectra of the synthesized complexes. In order to further probe the frontier orbitals of both complexes and study their redox behavior, each compound was separately characterized using cyclic voltammetry. The bulk electrolysis of a solution of complex 1 was analyzed by spectroscopic methods confirming the electrochemical synthesis of complex 2