Andrea Deák

Inclusion compounds containing a drug: structure and thermal stability of the first clathrates of nitrazepam and isothiocyanato ethanol complexes of Co(II) and Ni(II)

Abstract Syntheses, crystal structures and comparative analytical investigations on the first two inclusion compounds of an antiepileptic drug, nitrazepam (1,3-dihydro-7-nitro-5-phenyl-2H-1,4-benzodiazepin-2-one) are reported. The biologically active molecule forms isostructural clathrates with diaquadiethanolbis(isothiocyanato) complexes of both cobalt(II) and nickel(II) in molar ratios of 1:2 [M(NCS)2(C2H5OH)2(H2O)2]·2C15H11N3O3 (M=Co2+, 1, and M=Ni2+, 2). Detailed analyses of the structures, the secondary interactions, the neutral drug conformations, the FTIR spectra and thermal stabilities of the clathrates, in comparison with those of the crystalline nitrazepam, have been carried out. In the crystal structures there are only host–guest hydrogen bonds of O⋯H, N⋯H and S⋯H type. Owing to the comparable size of the two constituents neither host–host nor guest–guest secondary interactions occur. In the first thermal decomposition step a parallel release of ethanol and water was observed by simultaneous thermogravimetric and differential thermal analysis measurements. This indicates that some bonds of the metal complex unit and the host–guest secondary interactions in 1 and 2 are weaker than interactions in the pure drug. If an easy release of ethanol and water occurs during dissolution of 1 and 2, it might result in an improved bioavailability of the drug, which is soluble only in aqueous ethanol.

Synthesis and structure of a cyanoaurate-based organotin polymer exhibiting unusual ion-exchange properties.

We synthesized and structurally characterized the first cyanoaurate-based organotin polymer Me(3)Sn[Au(CN)(2)] (1), which exhibits unusual ion-exchange properties. In the structure of 1, the void space of the 2D grids formed via Au...Au bonding is filled by arrays of zigzag chains joined by weak Au...Au interactions. Interestingly, the practically insoluble polymer 1 shows unusual ion-exchange properties. The polymer Me(2)Sn[Au(CN)(2)](2) (2) was obtained in the metathesis reaction of 1 with Me(2)SnCl(2). Compound 2 displays cyanide-bridged uninodal four-connected 3D nets with 6(5).8 topology corresponding to the CdSO(4) prototype. Interestingly, 2 can be converted back into 1 by metathesis with Me(3)SnCl. Moreover, we performed a series of metal-exchange experiments in which 1 was soaked in aqueous solutions of bivalent transition-metal cations M(2+) (M = Co, Ni, Cu, Zn). As a result, 1 was completely converted into transition-metal cyanoaurates. To our knowledge, this represents the first study revealing the metal-exchange properties of a cyanoaurate-based heterometallic polymer.

Solvent-assisted spontaneous resolution of a 16-membered ring containing gold(I) showing short Au...Au aurophilic interaction and a figure-eight conformation.

The achiral 4,6-bis(diphenylphosphino) phenoxazine (nixantphos) ligand was used to synthesize a gold(I) complex, [Au2(nixantphos)2](NO3)2, containing a 16-membered [Au2(nixantphos)2](+2) cationic ring in a chiral figure-eight conformation. The single crystal X-ray diffraction analysis of [Au2(nixantphos)2](NO3)2.3MeOH.H2O (1) and [Au2(nixantphos)2](NO3)2.4MeCN (2) revealed a solvent-assisted spontaneous resolution of the [Au2(nixantphos)2](NO3)2 complex. By changing the nature of the solvent, homochiral hydrogen bonded helices (1) and heterochiral hydrogen bonded monomers (2) were obtained. Multinuclear NMR spectroscopy showed the evidence of chemical exchange phenomenon related to the interconversion of the enantiomeric skeletons of the 16-membered macrocycle in solution. The existence of the Au...Au aurophilic interaction was confirmed by the analysis of the spin-system in the (31)P NMR spectrum.

Anion‐, Solvent‐, Temperature‐, and Mechano‐Responsive Photoluminescence in Gold(I) Diphosphine‐Based Dimers

A series of [Au2 (nixantphos)2](X)2 (nixantphos=4,6-bis(diphenylphosphino)-phenoxazine; X=NO3, 1; CF3 COO, 2; CF3 SO3, 3; [Au(CN)2], 4; and BF4, 5) complexes that exhibit intriguing anion-switchable and stimuli-responsive luminescent photophysical properties have been synthesized and characterized. Depending on their anions, these complexes display yellow (3), orange (4 and 5), and red (1 and 2) emission colors. They exhibit reversible thermo-, mechano-, and vapochromic luminescence changes readily perceivable by the naked eye. Single-crystal X-ray studies show that the [Au2 (nixantphos)2](2+) cations with short intramolecular Au⋅⋅⋅Au interactions are involved as donors in an infinite N-H⋅⋅⋅X (X=O and N) hydrogen-bonded chain formation with CF3 COO(-) (2 C) and aurophilically linked [Au(CN)2](-) counterions (4 C). Both crystals show thermochromic luminescence; their room temperature red (2 C) and orange (4 C) emission turns into yellow upon cooling to 77 K. They also exhibit reversible mechanochromic luminescence by changing their emission color from red to dark (2 C), and orange to red (4 C). Compounds 1-5 also display reversible mechanochromic luminescence, altering their emission colors between orange (1) or red (2) to dark, as well as between yellow (3) or orange (4 and 5) to red. Detailed photophysical investigations and correlation with solid-state structural data established the significant role of NH⋅⋅⋅X interactions in the stimuli-responsive luminescent behavior.

A versatile solvent-free mechanochemical route to the synthesis of heterometallic dicyanoaurate-based coordination polymers.

The solid-state mechanochemical method was proved to be a fast, simple, and efficient route to the synthesis of heterometallic [Au(CN)(2)]-based coordination polymers. Thus, a series of mixed-metal complexes, such as KCo[Au(CN)(2)](3), KNi[Au(CN)(2)](3), Cu(H(2)O)(2)[Au(CN)(2)](2), and Zn[Au(CN)(2)](2), was obtained by grinding stoichiometric amounts of K[Au(CN)(2)] and transition metal(II) chlorides. This solid-state method rapidly yields pure dicyanoaurate-based compounds, also in cases when the aqueous solution synthesis leads to an unseparable mixture of products. In addition, in some cases, the solid state reaction was faster than the corresponding solvent-based reaction. This mechanochemical method can be applied also to main group metals to obtain various cyanoaurate-based heterometallic coordination polymers, such as Me(2)Sn[Au(CN)(2)](2) and Ph(3)Sn[Au(CN)(2)]. For the 2:1 mixture of K[Au(CN)(2)] and Me(2)SnCl(2), the dramatic enhancement of the reaction rate by the presence of a minor amount of water was noticed. In Ph(3)Sn[Au(CN)(2)], as was revealed by single-crystal X-ray diffraction, each Ph(3)Sn unit is linked to two others by two Au(CN)(2) bridges via Sn-N bonds to form an infinite cyanide-bridged chain. There are no Au···Au contacts between the chains due to the sterical hindrance of the phenyl groups. A dehydrated blue Co[Au(CN)(2)](2) complex was obtained during grinding or heating of the moderate-pink Co(H(2)O)(2)[Au(CN)(2)](2) complex. This complex displays a vapochromic response when exposed to a variety of organic solvents, as well as water and ammonia vapors.

Guest escape and uptake in nonporous crystals of a gold(I) macrocycle

The nonporous gold(I) diphosphine complex [Au(2)(cis-dppe)(2)](NO(3))(2) [1, cis-dppe = cis-1,2-bis(diphenylphosphino)ethylene] is robust enough to trap guests, but at the same time, it is flexible enough to allow guest release without destruction of its crystal lattice. This nonporous gold(I) compound 1 is also efficient at capturing and releasing carbon dioxide in a controlled manner.

A stimuli-responsive double-stranded digold(I) helicate

We report herein a stimuli-responsive dinuclear double stranded [Au2L2]2+ helicate assembled from gold(I) atoms and phenyl-substituted diphosphine ligands derived from a xanthene-type backbone (L). The conformational flexibility of the dinuclear [Au2L2]2+ helicate allows a diversity of molecular conformations and packing arrangements that lead to different solid-state emission colours. Blue (IB), bluish green (IIG) and yellow (IIIY) emitting crystalline and red emitting (IVR) amorphous forms of this double stranded [Au2L2]2+ helicate have been obtained by slight modification of the crystallization conditions. Different molecular conformations and packing arrangements of dinuclear double stranded [Au2L2]2+ helicates that result in different non-covalent interactions played the most significant role in tailoring the solid-state luminescence properties. On the basis of the single crystal structural data and photophysical studies, we found that an increasing number of intra- and mainly intermolecular noncovalent interactions locked and rigidified the twisted conformation of the double stranded [Au2L2]2+ helicate, and enhanced π-stacking between its aromatic units induced the red-shift in solid-state luminescence emission. The solid-state luminescence colour of this double stranded [Au2L2]2+ helicate can be switched reversibly from blue to red by external (mechanical and chemical) stimuli.

Self-assembly of gold(I) with diphosphine and bitopic nitrogen donor linkers in the presence of trifluoroacetate anion: formation of coordination polymer versus discrete macrocycle

The rigid Au2(dppbz)(CF3COO)2 (1) precursor (dppbz = 1,2-bis(diphenylphosphino)benzene) with preorganised syn-gold(I) centers has been self-assembled with 4,4′-bipyridyl (bipy) and 1,2-trans-bis(4-pyridyl)-ethylene (bipyen) to afford different supramolecular architectures: a unique [Au2(dppbz)(bipy)]n(CF3COO)2n (2) coordination polymer and a discrete [Au4(dppbz)2(bipyen)2](CF3COO)4 (3) macrocycle in response to changes in bitopic nitrogen donor linker.

Synthesis and Structural Characterization of Tin(IV) N‐nitroso‐N‐phenylhydroxylaminato Complexes: Crystal Structures of Sn(O2N2Ph)4, Ph2Sn(O2N2Ph)2 and [Me2Sn(O2N2Ph)2]2

Reaction of cupferron [NH4L, L = PhN(O)NO–] with tin(IV), diphenyltin(IV) and dimethyltin(IV) halides yields the cupferronato complexes SnL4 (1), Ph2SnL2 (2) and [Me2SnL2]2 (3). All were characterized by FT-IR, FT-Raman, NMR (1H, 13C and 119Sn) spectroscopic methods and X-ray structural analysis. An almost ideal, very rare dodecahedral geometry is found in the structure of 1. The hexacoordinated tin center exhibits a bicapped tetrahedral geometry in complex 2. The tin centers are heptacoordinated in a pentagonal bipyramidal geometry in the dimeric complex 3. These complexes incorporate five-membered SnO2N2 and four-membered Sn2O2 inorganic rings. Vibrational spectral data are consistent with the structures determined. The 119Sn NMR spectra indicate that in solution 1 retains its octacoordinated nature; in compound 2 the tin atom is hexacoordinated, while in 3 the tin atom is pentacoordinated.

A new inorganic (carbon-free) chelate ring: SnO2N2. Eight-coordinated tin(IV) in Sn(O2N2Ph)4 and a self-assembled 20-membered macrocycle in [Me3Sn(O2N2Ph)]4

Abstract The reaction of cupferron (NH4L, L=PhN(O)NO−) with tin(IV) and trimethyltin(IV) halides yields cupferronato complexes SnL4 (1) and [Me3SnL]4 (2) which were characterised by FT-IR and FT-Raman spectroscopy. The first X-ray diffraction analysis of the complexes reveals a slightly distorted dodecahedral and trigonal-bipyramidal coordination of the central metal atoms in 1 and 2, respectively. The N-nitroso-N-phenylhydroxylaminato [PhN(O)NO−] ligand behaves as chelating in 1 and bridging in 2 leading to a novel five-membered chelate ring, SnO2N2 in 1 and an unprecedented 20-membered inorganic metallomacrocycle, Sn4O8N8 in 2.