Antonio Laguna

Combining Aurophilic Interactions and Halogen Bonding To Control the Luminescence from Bimetallic Gold−Silver Clusters

The luminescence in a series of new bimetallic gold-silver vapochromic structures can be efficiently switched among different colors simply by exposure to solvent vapors. The emission color in these systems is controlled by both aurophilic interactions and halogen bonding, which affect the emission energy through different orbitals.

Novel anionic gold(I) and gold(III) organocomplexes

Summary Tetrahydrothiophen (tht) and/or chloride may readily be displaced from ClAu(tht) with perhaloaryl lithium to give anionic complexes of the [R 2 Au] − or [RAuX] − type (R = C 6 F 5 or C 6 Cl 5 ; X = Cl or Br). Anionic gold(III) complexes can be prepared both by the reaction of Cl 3 Au-(tht) or K[AuCl 4 ] with LiC 6 F 5 or by the oxidative addition of halogens or (C 6 F 5 ) 2 TlBr to gold(I) complexes.

Making the golden connection: reversible mechanochemical and vapochemical switching of luminescence from bimetallic gold-silver clusters associated through aurophilic interactions.

Aiming at the development of new architectures within the context of the quest for strongly luminescent materials with tunable emission, we utilized the propensity of the robust bimetallic clusters [Au₂Ag₂(R(I)/R(II))₄] (R(I) = 4-C₆F₄I, R(II) = 2-C₆F₄I) for self-assembly through aurophilic interactions. With a de novo approach that combines the coordination and halogen-bonding potential of aromatic heteroperhalogenated ligands, we have generated a family of remarkably luminescent bimetallic materials that provide grounds to address the relevance, relative effects, and synergistic action of the two interactions in the underlying photophysics. By polymerizing the green-emitting (λ(max)(em) = 540 nm) monomer [Au₂Ag₂R(II)₄(tfa)₂]²⁻ (tfa = trifluoroacetate) to a red-emitting (λ(max)(em) = 660 nm) polymer [Au₂Ag₂R(II)₄(MeCN)₂](n), we demonstrate herein that the degree of cluster association in these materials can be effectively and reversibly switched simply by applying mechanochemical and/or vapochemical stimuli in the solid state as well as by solvatochemistry in solution, the reactions being coincident with a dramatic switching of the intense, readily perceptible photoluminescence. We demonstrate that the key event in the related equilibrium is the evolution of a metastable yellow emitter (λ(max)(em) = 580 nm) for which the structure determination in the case of the ligand R(II) revealed a dimeric nonsolvated topology [Au₂Ag₂R(II)₄]₂. Taken together, these results reveal a two-stage scenario for the aurophilic-driven self-assembly of the bimetallic clusters [Au₂Ag₂(R(I)/R(II))₄]: (1) initial association of the green-emitting monomers to form metastable yellow-emitting dimers and desolvation followed by (2) resolvation of the dimers and their self-assembly to form a red-emitting linear architecture with delocalized frontier orbitals and a reduced energy gap. The green emission from [Au₂Ag₂R(II)₄(tfa)₂]²⁻ (λ(max)(em) = 540 nm) exceeds the highest energy observed for [Au₂Ag₂]-based structures to date, thereby expanding the spectral slice for emission from related structures beyond 140 nm, from the green region to the deep-red region.

Vapochromic behavior of {Ag2(Et2O)2[Au(C6F5)2]2}n with volatile organic compounds.

The vapochromic behaviors of {Ag2L2[Au(C6F5)2]2}n (L = Et2O (1), Me2CO (2), THF (3), CH3CN (4)) were studied. {Ag2L2[Au(C6F5)2]2}n (L = Et2O (1)) was synthesized by the reaction of [Bu4N][Au(C6F5)2] with AgOClO3 in 1:1 molar ratio in CH2Cl2/Et2O (1:2). 1 was used as starting material with THF to form {Ag2L2[Au(C6F5)2]2}n (L = THF (3)). 3 crystallizes in the monoclinic space group C2/c and consists of tetranuclear units linked together via aurophilic contacts resulting in the formation of a 1D polymer that runs parallel to the crystallographic z axis. The gold(I) atoms are linearly coordinated to two pentafluorophenyl groups and display additional Au...Ag close contacts within the tetranuclear units with distances of 2.7582(3) and 2.7709(3) A. Each silver(I) center is bonded to the two oxygen atoms of the THF molecules with a Ag-O bond distance of 2.307(3) A. TGA analysis showed that 1 loses two molecules of the coordinated solvent per molecular unit (1st one: 75-100 degrees, second one: 150-175 degrees C), whereas 2, 3, and 4 lose both volatile organic compounds (VOCs) and fluorinated ligands in a less well defined manner. Each complex loses both the fluorinated ligands and the VOCs by a temperature of about 325 degrees C to give a 1:1 gold/silver product. X-ray powder diffraction studies confirm that the reaction of vapors of VOCs with 1 in the solid state produce complete substitution of the ether molecules by the new VOC. The VOCs are replaced in the order CH3CN > Me2CO > THF > Et2O, with the ether being the easiest to replace. {Ag2(Et2O)2[Au(C6F5)2]2}n and {Ag2(THF)2[Au(C6F5)2]2} n both luminesce at room temperature and at 77 K in the solid state. Emission maxima are independent of the excitation wavelength used below about 500 nm. Emission maxima are obtained at 585 nm (ether) and 544 nm (THF) at room temperature and at 605 nm (ether) and 567 nm (THF) at 77 K.

Structural characterization of silver(I) complexes [Ag(O3SCF3)(L)] (L=PPh3, PPh2Me, SC4H8) and [AgLn](CF3SO3) (n=2–4), (L=PPh3, PPh2Me)

Abstract We have studied the solution and some solid state structures of a series of trifluoromethanesulfonate silver(I) complexes, namely of formula [Ag(O3SCF3)(L)] (L=PPh3, PPh2Me, SC4H8) and [AgLn](CF3SO3) (n=2–4, L=PPh3, PPh2Me). The solution behaviour is as expected for mononuclear silver species, although polynuclear species can not be totally ruled out in non-coordinating solvents. The solid state structures display a wide variety of nuclearities, silver co-ordination numbers and trifluoromethanesulfonate co-ordination modes, depending on the ligand L. Thus, for complexes of empirical formula [Ag(O3SCF3)(L)], the crystal structure of [Ag(O3SCF3)(PPh3)] is a trimer with bridging triflates; the molecular structure of [Ag(O3SCF3)(PPh2Me)] shows tetranuclear complexes with a ‘chair’ geometry, further linked into chains by Ag–phenyl interactions; and [Ag(O3SCF3)(tht)] (tht=SC4H8) crystallizes in infinite chains. For complexes of formula [Ag(O3SCF3)(L)2], the PPh3 derivative is a dimer with two bridging triflates, and the PPh2Me derivative is a monomer.

New palladium(II) and platinum(II) complexes with 9-aminoacridine: structures, luminiscence, theoretical calculations, and antitumor activity.

The new complexes [Pd(dmba)( N10-9AA)(PPh 3)]ClO 4 ( 1), [Pt(dmba)( N9-9AA)(PPh 3)]ClO 4 ( 2), [Pd(dmba)( N10-9AA)Cl] ( 3), and [Pd(C 6F 5)( N10-9AA)(PPh 3)Cl] ( 4) (9-AA = 9-aminoacridine; dmba = N,C-chelating 2-(dimethylaminomethyl)phenyl) have been prepared. The crystal structures have been established by X-ray diffraction. In complex 2, an anagostic C-H...Pt interaction is observed. All complexes are luminescent in the solid state at room temperature, showing important differences between the palladium and platinum complexes. Complex 2 shows two structured emission bands at high and low energies in the solid state, and the lifetimes are in agreement with excited states of triplet parentage. Density functional theory and time-dependent density functional theory calculations for complex 2 have been done. Values of IC 50 were also calculated for the new complexes 1- 4 against the tumor cell line HL-60. All of the new complexes were more active than cisplatin (up to 30-fold in some cases). The DNA adduct formation of the new complexes synthesized was followed by circular dichroism and electrophoretic mobility. Atomic force microscopy images of the modifications caused by the complexes on plasmid DNA pB R322 were also obtained.

Synthesis and characterisation of copper complexes with N-ferrocenoyl-N′-aryl(alkyl)thioureas

Abstract The treatment of CuCl 2 ·2H 2 O with ferrocenoyl-substituted thioureas of the type FcC(O)NHC(S)N′HR (Fc=ferrocenyl; R=C 6 H 5 ; C 6 H 4 - p -OMe; C 6 H 4 - p -C(O)Me; C 6 H 4 - o -Me; C 6 H 4 - o -Cl; C 6 H 4 - o -NO 2 ; i -Pr) gives the corresponding copper(I) derivatives with the metallic centre in an unusual coordination mode. The complexes were characterised by spectroscopic methods and X-ray diffraction studies. The electrochemical behaviour of these compounds was also investigated.

Simple and efficient synthesis of [MCI(NHC)] (M = Au, Ag) complexes

A facile and efficient synthetic route leading to catalytically relevant N-heterocyclic carbene (NHC) gold complexes is described. The method consists of one pot synthesis starting from readily available imidazolium salts and [AuCl(tht)], in the presence of K2CO3. Using the same protocol NHC silver complexes have been synthesised starting from AgNO3.

Coordination chemistry of gold(II) complexes

Abstract The number of complexes with gold in a formal oxidation state of two have increased considerably and nowadays this oxidation state can be considered nearly as a common state in gold chemistry. This review covers the evolution of the knowledge of this oxidation state from the first dithiocarbamate derivatives [Au 2 (S 2 CNR 2 ) 2 X 2 ], stable only at very low temperature, to the room temperature stable dinuclear gold complexes [Au 2 (L–L) 2 X 2 ] (L–L=CH 2 PPh 2 CH 2 , CH 2 PPh 2 S, C 5 H 4 PPh 2 -2; X=halogen). Although a dinuclear structure with a gold(II)–gold(II) bond supported by two equal bridging ligands were the first and most common, this review shows the present diversity as mononuclear, [Au([9]aneS 3 ) 2 ](BF 4 ) 2 , dinuclear with two different bridging ligands, [Au 2 (S 2 CNR 2 )(CH 2 PPh 2 CH 2 )X 2 ], with a non-supported metal–metal bond, [Au 2 (Ph 2 PC 8 H 6 PPh 2 ) 2 Cl 2 ](PF 6 ) 2 , and polynuclear gold(II) complexes either with chains of only gold centers or with other metals, such as [{(C 6 F 3 H 2 )Au(CH 2 PPh 2 CH 2 ) 2 Au} 2 Au 2 (CH 2 PPh 2 CH 2 ) 2 ]ClO 4 or [Au 2 Pt(CH 2 PPh 2 S) 4 X 2 ]

Anionic perfluorophenyl complexes of gold(I) and gold(III)

Abstract The preparation of organogold(I) anions of the types [AuRX]−, [AuR2]− and [AuRR′]− (R,R′ = C6F5 or 2,4,6,-C6F3H2; X = Cl, i, SCN. CN or N3) is accomplished in which the tetrahydrothiophen group of AuR(tht) is substituted by X,R or R′. Oragnogold(III) complexes of the general formulae [Aur2X2]−, [AuRR′X2]−, [AuR3X]− and [AuR4]− (R, R′ = C6F5, 2,3,4,6-C6F4H or 2,4,6,-C6F3H2; X = Cl, Br or I) are obtained either by oxidation of the above-mentioned gold(I) complexes or by substitution reactions of AuCl3(tht). The assignment of the cis- or, respectively, trans-configuration of the [AuR2X2]− derivatives is based on their IR spectra.