Giulia Cantoni

Water vapour uptake and extrusion by a crystalline metallorganic solid based on half-sandwich Ru(II) building-blocks

The X-ray structure of the half-sandwich Ru(II) complex [(p-cymene)Ru(κN-INA)Cl2] (INA = isonicotinic acid) (1α) does not show the expected cyclic dimerization of the carboxylic functions of INA. The good hydrogen bond accepting character of the chloride ligand in fact, leads to the formation of Ru–Cl⋯HOOC intermolecular hydrogen bonded chains. Interestingly, 1α quickly converts into the hydrated form [(p-cymene)Ru(κN-INA)Cl2]H2O (1·H2O) once exposed to water vapours through a heterogeneous solid-gas reaction. In the X-ray structure of 1·H2O two water molecules bridge two carboxylic functions of two different organometallic entities, giving rise to a R44(12) cyclic dimer. The 1α to 1·H2O transformation occurs smoothly even when the first is exposed to vapours of absolute ethanol, whose water content is not higher than 0.2%. The thermally induced dehydration of 1·H2O does not give 1α back, but rather it leads to a not yet defined transient species (1γ) which finally transforms into a polymorphic form of 1α, whose solid state structure has been solved by X-ray powder diffraction analysis (1β).

Synthesis, characterization and biological activity of three square-planar complexes of Ni(II) with ethyl (2E)-2-[2-(diphenylphosphino)benzylidene]hydrazinecarboxylate and monodentate pseudohalides.

Three square-planar complexes of nickel(II) with the tridentate condensation derivative of 2-(diphenylphosphino)benzaldehyde and ethyl carbazate, and monodentate pseudohalides, have been synthesized. Their crystal structures have been determined. All the complexes showed a significant antifungal activity, while only the azido complex displayed antibacterial activity. All the complexes were cytotoxic to a panel of six tumor cell lines, the azido complex showing a similar activity as cisplatin to leukemia cell line K562 and lower toxicity to normal MRC-5 cells than that anticancer agent. The complexes interfered with cell cycle of tumor cells and induced plasmid DNA cleavage.

Exploration of Supramolecular Synthons and Molecular Recognition Starting from Macroscopic Measurements of Crystal Dimensions

The complete control over the fabrication of crystalline materials is focused nowadays on a bottom-up philosophy that ideally starts with the design and synthesis of good building blocks for assembling a functional material, proceeds with the prediction of how the molecular units will self-assemble in the crystal, deals with the nucleation of the correct crystal form, continues with the growth of final materials with a predetermined shape, and ultimately relates macroscopic properties to the geometry and strength of the intermolecular interactions. Here we explore the reverse approach: we analyze and measure the macroscopic morphologies of crystals of a single organometallic compound (1) obtained from different solvents in order to identify and rank the intermolecular forces responsible for molecular selfrecognition, and then we test and quantify how the functional groups of 1 interact with different solvents. Compound 1 was crystallized from six different purified solvents (CH2Cl2, CH3NO2, CH3OH, n-CH3CH2CH2OH, CH3CN, CH2Cl2/H2O), giving the same monoclinic nonsolvate crystals, whose nicely faceted morphology is defined by the four forms {001}, {010}, {1̄01}, and {1̄11} (a form is the collection of all faces equivalent by symmetry; Figure 1). Compound 1 always crystallizes in platelets, with a prominent basal pair of faces form {001}, and a lateral envelope made up of the other three forms, which develop to different extents depending upon the solvent used. This suggests that molecular recognition at the solid–solution interface during crystal growth is very effective for the chemical groups exposed at the surfaces constituting the lateral forms, and points to kinetic control of the final shape. A reliable description of molecular recognition processes in organometallic compounds is particularly difficult, as these compounds with so many electrons are too demanding for state-of-the-art protocols of crystal structure prediction. In fact, 1 contains many functional groups that can function as supramolecular synthons. While it is well known that the presence of a metal center alters the electron distribution in the ligands and influences heavily the energy of intermolecular interactions, most of the recent studies on the crystal packing of organometallic compounds are based on purely geometrical considerations, and few reports deal with the energy of the supramolecular interactions. We have investigated the supramolecular synthons that stabilize the crystal packing of 1 without relying on considerations of intermolecular distances, which in some cases have been questioned. According to Hartman and Perdok, the {hkl} forms shown in Figure 1 should consist of the slowest growing flat faces. These are stable slices of molecules assembled by at least two nonparallel arrays [uvw] of strong supramolecular interactions (periodic bond chains) running along the layer (Figure 2a). We assume that these arrays are built by the most important supramolecular synthons that connect pairs of molecules aligned along [uvw] in the crystal packing of 1. By analyzing the stereographic projection (see the Supporting Information) we can deconvolute four main directions [uvw] of molecular arrays that build up the observed crystal faces (hkl) and consequently define the principal supramolecular synthons (SYN) for 1 (Figure 3). Remarkably, while molecular pairs running along [010] could have easily been labeled as hydrogen bonds [SYN1 OH···Cl (1/2 x,y 1/2,1/ 2 z) = 3.170(1) , 161(2)8 ; SYN2 CH···Cl ( 1/2 x,y 1/2,1/ 2 z) = 3.534(2) , 124(1)8] by a routine analysis of the packing (see the Supporting Information), intermolecular contacts SYN3 along [100] (minimum C···C = 3.567 ) and Figure 1. Morphologies of 1 a) depending on the solvent (ROH: CH3OH and n-CH3CH2CH2OH give the same morphology) and b) averaged on different crystals for each crystallization experiment; c) ideal morphology, calculated as described in the text.

Hydrogen-bond networks in polymorphs and solvates of metallorganic complexes containing ruthenium and aminoamide ligands

Half-sandwich ruthenium(II) complexes containing the two amino-amide ligands 4-aminobenzamide (4AB) and 4-aminobenzanilide (4ABN) have been synthesized and structurally characterized. The complexes have the general formula {[(p-cymene)RuCl2(κN-ligand)](x·solvent)}. The crystal packings are governed by extended hydrogen-bond networks involving the N–H bonds of the amine and amide groups as well as the Cl ligands. In the case of 4AB, two different non-solvate polymorphs (x = 0) have been isolated from methanol (1α) and water (1β, disappearing polymorph). In both cases, the amide groups of two molecules associate, giving rise to a supramolecular ring, where the N–H bond not involved in the ring intermolecularly contacts a neighbouring Cl ligand. The resultant frameworks are very robust, thus impeding the insertion of solvent molecules. A methanol-solvate (1·MeOH) has in fact been isolated in very low yield where two methanols bridge two different amide groups. These crystals are highly unstable at room temperature. However, 1α shows a distinct reactivity toward NH3 in heterogeneous gas-uptake experiments, although the final nature of the product has not yet been defined. A comparison between the structural results reported here and those previously collected with 4-aminobenzoic acid reveals that the COOH function leads to linear supramolecular wheel-and-axle motifs, while the C(O)NH2 function of 4AB leads to bent supramolecular wheel-and-axle motifs. The complexes containing 4ABN (2 and 2·2H2O) have always been crystallized as solvate (2·EtOH and 2·H2O), where the included guest molecules are hydrogen-bonded to the C(O)NHR functionality, thus preventing the dimerization of the amide groups.

Synthesis, characterization, DFT calculations, and antimicrobial activity of Pd(II) and Co(III) complexes with the condensation derivative of 2-(diphenylphosphino)benzaldehyde and Girard’s T reagent

Complexes of Pd(II) and Co(III) with the condensation derivative of 2-(diphenylphosphino)benzaldehyde and Girard T reagent were synthesized, characterized, and their antimicrobial activities were evaluated. The ligand and the complexes were characterized by elemental analysis, IR and NMR spectroscopies, and X-ray crystallography. In both complexes, the deprotonated ligand was coordinated to the metal through the phosphorus, the imine nitrogen, and the carbonyl oxygen atoms. In the octahedral Co(III) complex, two molecules of ligands were coordinated to metal ion, while square-planar environment of Pd(II) complex was constituted of one tridentate ligand and chloride in the fourth coordination place. The ligand and complexes showed moderate antibacterial activity. The molecular structures of the obtained metal complexes and the relative stabilities of two stereoisomers of the ligand were calculated using density functional theory at the S12g/TZ2P level. Graphical Abstract

A discussion on the solid state organization of 4-pyridyl imino compounds and on the co-crystallization between their molecular precursors

The synthesis and the crystal structures of several 4-pyridyl imino compounds are reported. Their solid-state organization is based on head-to-tail chains sustained by O–H⋯N hydrogen bonds; the supramolecular arrangement is analysed by means of the Hirshfeld surfaces and of the corresponding 2D-fingerprint plots. The co-crystallization between 4-aminobenzyl alcohol and 4-acetylpyridine is analysed, correlating reactivity trends and structural characters. In this context, the single crystal X-ray diffraction analyses of 4-aminobenzyl alcohol and 3,5-diphenyl-4-hydroxyaniline are also reported.

Polymorphs and co-crystal with half-sandwich Ru(II) dimers [(η6-arene)RuX2]2

The solid-state organization of the two important metallorganic precursors [(η6-p-cymene)RuI2]2 and [(η6-indane)RuCl2]2 is studied herein. Single crystals of [(η6-indane)RuCl2]2 have been obtained by slow evaporation of a dichloromethane solution of the dimeric complex, while two polymorphs of [(η6-p-cymene)RuI2]2 were obtained by modifying the conditions of the crystallization experiments. In addition, the reaction between [(η6-p-cymene)RuCl2]2 and 4-(N-methylamino)benzoic acid in methanol led unexpectedly to the isolation of a co-crystal where the amine ligand interacts with the organometallic dimer through an intermolecular N–H⋯Cl–Ru hydrogen bond. The most important features of the packing of all these compounds are described and compared with analogous crystal forms already present in the Cambridge Structural Database in order to derive general information on the aggregation modes of [(η6-arene)RuX2]2 systems.