Synthesis, structure diversity, and antimicrobial studies of Ag(i) complexes with quinoline-type ligands

Compounds [Ag(5NO2Qu)2]BF4 (1) and [Ag(Qu3CN)(H2O)]BF4 (2) were prepared and studied from a structural perspective and screened for antimicrobial activity. The Ag(i) in the monomeric complex 1 is coordinated to two 5-nitroquinoline (5NO2Qu) ligands via the N-atoms of the quinoline rings with equidistant Ag-N bonds (2.146(2) \uc5) and a N-Ag-N# bond angle of 171.42(8)\ub0. The 2D coordination polymer 2 contains tetracoordinated Ag(i) with two N-atoms (N1 and N2#1) from two quinoline-3-carbonitrile (Qu3CN) ligands and two O-atoms (O1 and O1#1) from two water molecules. The Qu3CN ligand acts as a connector between the Ag(i) sites along the b-direction via two short Ag1-N1 (2.185(4) \uc5) and Ag1-N2#1 (2.204(4) \uc5) bonds. In addition, the Ag(i) is coordinated with two symmetry related water molecules which are also acting as connectors between the Ag(i) sites along the a-direction via two longer Ag1-O1 (2.470(4) \uc5) and Ag1-O1#2 (2.546(4) \uc5) bonds. Hirshfeld surface analysis confirmed the significance of the polar F⋯H contacts in the molecular packing of 1 (25.9%) and 2 (39.9%). In addition, the crystal packing of 1 showed a significant amount of polar O⋯H (23.5%) contacts. Also, both complexes displayed π-π stacking interactions. The Ag(i) complexes and the free ligand were assessed for their antimicrobial activities. It was found that 1 (MIC = 7.8 μg mL−1) and 2 (MIC = 31.25 μg mL−1) have higher antifungal potency against C. albicans than their free ligands (MIC = 125 μg mL−1). Interestingly, 1 has better antifungal activity than the standard nystatin (15.6 μg mL−1). Also, both Ag(i) complexes and the free ligands as well have better activity against P. mirabilis than the common antibiotic amoxicillin

Exploring the impact of select anchor groups for norbornadiene/quadricyclane single-molecule switches

To achieve the ultimate limit of device miniaturization, it is necessary to have a comprehensive understanding of the structure-property relationship in functional molecular systems used in single-molecule electronics. This study reports the synthesis and characterization of a novel series of norbornadiene derivatives capped with thioether and thioester anchor groups. Utilizing the mechanically controllable break junction technique, the impact of these capping groups on conductance across single-molecule junctions is investigated. Among the selection of anchor groups, norbornadiene capped with thioacetate and tert-butyl groups exhibits higher conductance (G ≈ 4 × 10−4 G0) compared to methyl thioether (G ≈ 2 × 10−4 G0). Electronic transmission through the considered set of single-molecule junctions has been simulated. The computational results for electron transport across these junctions align closely with the experimental findings, with the thioacetate- and tert-butyl-substituted systems outperforming the methyl thioether-capped derivative. In terms of junction stability, the methyl thioether-capped system is the most resilient, maintaining consistent conductance even after approximately 10 000 cycles. Meanwhile, the likelihood of observing molecular plateaus in both the thioacetate- and tert-butyl-substituted systems declines over time. These findings substantially advance both the design and understanding of functional molecular systems in the realm of single-molecule electronics, particularly in the context of molecular photoswitches.KMP acknowledges funding from the Catalan Institution for Research and Advanced Studies (ICREA), the European Research Council (ERC) through ERC-CoG PHOTHERM, and the European Union project ESiM 101046364. The Swedish NMR Centre at the University of Gothenburg is acknowledged for its support.With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).Peer reviewe

Salts of phenylacetic acid and 4-hydroxyphenylacetic acid with Cinchona alkaloids: Crystal structures, thermal analysis and FTIR spectroscopy

Seven salts were formed with phenylacetic acid (PAA), 4-hydroxyphenylacetic acid (HPAA) and the Cinchona alkaloids; cinchonidine (CIND), quinidine (QUID) and quinine (QUIN). For all the structures the proton was transferred from the carboxylic acid of the PAA/HPAA to the quinuclidine nitrogen of the respective Cinchona alkaloid. For six of the salts, water was included in the crystal structures with one of these also incorporating an isopropanol solvent molecule. However HPAA co-crystallised with quinine to form an anhydrous salt, (HPAA−)(QUIN+). The thermal stability of the salts were determined and differential scanning calorimetry revealed that the (HPAA−)(QUIN+) salt had the highest thermal stability compared to the other salt hydrates. The salts were also characterized using Fourier transform infrared spectroscopy. (PAA−)(QUID+)·H2O and (PAA−)(QUIN+)·H2O are isostructural and Hirshfeld surface analysis was completed to compare the intermolecular interactions in these two structures.National Research Foundation (South Africa) and the Cape Peninsula University of Technology

Halogen Bonding in Host–Guest Compounds: Structures and Kinetics of Enclathration and Desolvation

The host compounds tetrakis­(4-bromophenyl) ethylene and its iodo-analogue form inclusion compounds with a series of chloro- and iodo-methanes. Their structures have been elucidated, and their nonbonded halogen···halogen contacts have been analyzed and classified. Their kinetics of desolvation have been studied, and the concomitant activation energies have been established. Five of the clathrates are isostructural and display similar activation energies of desolvation, thus correlating structure and function. The velocity of the enclathration for the solid host–methyl iodide vapor reactions and associated rate law have been established

Pore size effect of 1,3,6,8-tetrakis(4-carboxyphenyl)pyrene-based metal-organic frameworks for enhanced SF6 adsorption with high selectivity

Anthropogenic greenhouse gas emission poses as serious threat to our environment and it is therefore of utmost importance that efficient systems are developed to mitigate these issues. SF6, in particular, has attracted more attention in recent years due to its global warming potential which severely exceeds that of CO2. In this study we present the SF6 sorption properties of four highly porous 1,3,6,8-tetrakis(4-carboxyphenyl)pyrene-based (TBAPy4−) metal-organic frameworks containing either ytterbium(III), thulium(III), cerium(III), or hafnium(IV). These MOFs can be synthesized with high crystallinity in as little as 5 h and were found to have good SF6 uptakes due to their suitable pore size. The SF6 uptake of the Yb-TBAPy MOF reached 2.33 mmol g−1 with high Henry's law SF6-over-N2 selectivity of ∼80 at 1 bar and 293 K. The TBAPy-MOFs were also found to have good chemical stability and good cyclic SF6 sorption stability with fast SF6 uptake. These TBAPy-MOFs possesses many of the properties desired for an efficient SF6 sorbent and may be suitable sorbents for further development, including sorbent processing for industrial applications

The Open and Closed Forms of a Perfluoro Diarylethene PhotoswitchHalogen Bonding, Network Topology, and CSD Analysis

The structure of the perfluoro cyclopentene diarylethene photoswitch 3,3′-(perfluorocyclopent-1-ene-1,2-diyl)bis(2-ethyl-6-iodobenzo[b]thiophene 1,1-dioxide) (C25H16F6I2O4S2) 1 at 100 K has a tetragonal (I41/a) symmetry. The compound has a halogen-bonded network structure described by the uninodal five-connected joa net. This net is related to another uninodal six-connected net sfo. Analysis using the Cambridge Structural Database (CSD) shows that the majority of structures with the perfluoro cyclopentene diarylethene motif, >85%, have a C···C distance of around 3.5 Å where a new single bond will develop during photoswitching, whereas compound 1 falls in a second smaller category with C···C distances of around 4.2 Å. The photochemical reaction of 1 under UV light in ethanol gave a closed form that crystallized as ethanol solvate 2a in the P21/c space group, and recrystallization in acetone gave the nonsolvated form 2b crystallizing in the space group Fdd2. We did not observe, and do not believe that it is possible, to photoswitch 1 in the solid state as the C···C distance where a new single bond will develop is very long

Secondary Interactions in Halogenated Werner Clathrates

Halogenated Werner clathrates which contain Cl, Br, and I as part of the host and guest moieties have been synthesized and characterized by single X-ray diffraction, thermal analysis, and solid–vapor kinetics of formation. The compounds derived from NiI₂ are ionic, forming I^– salts and which yielded tri-iodide anions by the addition of I₂. Secondary interactions involving halogen···halogen and hydrogen bonds have been fully characterized and the structures were correlated with the thermal decomposition results

Guest Exchange in Halogenated Host–Guest Compounds: Structures and Kinetics

The host compounds tetrakis­(4-bromophenyl) ethylene, <b>H1</b>, and its iodo-analogue (<b>H2</b>) form inclusion compounds with the guests 1,2-dichloroethane (DCE), methyl iodide (MeI), benzene (BEN), and piperidine (PIP). The structures of the host–guest compounds have been elucidated and a series of exchange experiments on these compounds were performed by exposing their single crystals to the vapors of different guests. The kinetics of the exchange was monitored by NMR spectroscopy, and the reactions were interrupted and the structures of the inclusion compounds containing both the incoming and outgoing guests were solved. In the case of <b>1.5H1·DCE</b> exchanged with MeI, the intermediate structure yields a unit cell which has quadrupled in volume and shows both DCE and MeI in distinct, different locations. In the case of BEN being exchanged with PIP, the guests occupy the same site, and the mechanism is one of isomorphous replacement

Halogen-Bonding, Isomorphism, Polymorphism, and Kinetics of Enclathration in Host–Guest Compounds

The inclusion compounds formed by the host tetrakis­(4-bromphenyl) ethylene and its iodo-analogue have been characterized. Their structures have been elucidated and the halogen···halogen interactions recorded. The iodo-host forms two polymorphs with 3-picoline and their structures have different void topologies which correlate with the corresponding DSC profiles. The kinetics of enclathration by the bromo-host was carried out in aqueous suspension for the 3-picoline and the 3-brompyridine guests yield distinctly different results

A unified topology approach to dot-, rod-, and sheet-MOFs

Metal-organic frameworks made from multi-metal-ion units in the shape of clusters and rods (termed dot-MOFs and rod-MOFs) are well known. Here, we introduce MOFs with multi-metallic units in the form of sheets—sheet-MOFs. We show exemplars of all three types of units based on structures containing Y3+, Ce3+, or Gd3+ linked by benzene-1,2,4,5-tetracarboxylate to give crystals of a dot-MOF in H2NMe2[Y(btec)(H2O)] CTH-14, a sheet-MOF in [Ce3(btec)(Hbtec)(OAc)(HCO2)] CTH-15, and a rod-MOF in 4,4′-azopyridinium[Gd2(btec)2] CTH-16. Cyclic voltammetry shows that CTH-15 stabilizes Ce(IV). Given the fact that sheet-MOFs represent an intellectual advance in the evolution of MOFs, a unified approach is proposed for the topological classification of dot-, rod-, and sheet-MOFs. It is suggested that the stability of MOFs follow in the trend dot &lt; rod &lt; sheet. For CTH-14-16, the sheet- and the rod-MOF have higher thermal stability. We suggest sheet-MOFs as an additional strategy for making robust MOFs