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Complexation of the green bismuthinidene (RBi) with two equivalents of a highly fluorinated aryl iodide at low temperature allows the crystallographic identification of an unstable red species that can be regarded as an intermediate in an overall Bi(I) → Bi(III) oxidation process. Both C–I bonds are orientated toward the filled 6p orbital of bismuth (Bi–I distances 3.44–3.52 Å), leading to an elongation of the C–I bonds by 0.05 and 0.07 Å. Density functional theory (DFT) calculations confirm that the Bi(I) center is indeed acting as an electron donor, establishing two strong and directional halogen bonds. The color change from green to red upon halogen bond formation is a consequence of the energetic stabilization of a Bi(I) lone pair by interactions with the sigma-holes of the halogen bond donors. Overall, this study presents the first structural proof of bismuth, and more generally of heavy organopnictogen(I) compounds, acting as halogen bond acceptors.

The experimental realization of a variety of multimetallic systems composed by transition metals (TM) and heavier pnictogens has been widely explored via σ-bond activation of dipnictanes (Pn2R4), or even poly pnictanes (cyclo-(RnPn)n, Pn = Sb and Bi and R = any substituent). In contrast, isolation of stable metallacyclic rings viaTM-mediated activation of Sb and Bi multiple bonds are underexplored. Here, we reported the reactivity of “Sb = Sb” and “Bi = Bi” compounds with Jonas’ complex (CpCo(C2H4)2, Cp = C5H5) as the key electrophile to generate the “Co-Pn2” unit. Further exploiting of the synthetic potential of complex 2using various reagents led to a series of stable multimetallic compounds (5, 6, and 7) containing low-valent heavy pnictogens. These findings have been supported by a thorough investigation of the electronic features of these multimetallic complexes.

In this study, we report the syntheses of two new coordination polymers (CPs) of Mn(II) and Co(II), [Mn(4-avp)2(adc)(H2O)]·(solvent)x(1) and [Co(4-avp)2(adc)(CH3OH)2] (2), respectively, using relatively less explored linear linker acetylenedicarboxylic acid (H2adc) and polyaromatic hydrocarbon (PAH)–based monodentate N-donor ligand 4-[2-(9-anthryl)vinyl]pyridine (4-avp). CP1creates a two-dimensional (2D) structure in this instance, while CP2is made up of a 1D chain polymer. It is of interest that CP1and CP2exhibit semiconducting behavior and behave as Schottky barrier diodes. However, CP1exhibits higher conductivity and better Schottky diode formation when compared to CP2, which relates to the charge transportation through space via π···π interactions present in CP1. The experimental results are well validated by theoretical density functional theory (DFT) prediction based on band gap and density-of-state (DOS) calculations. It is noteworthy that fabrication of Mn/Co-based Schottky devices appears to be inadequate in the literature. Thus, this work showcases a new direction for the development of electronic device fabrication.

This work synthesized two Hg complexes (1–2) using a LO-richligand (LO-rich= LO-VAN/LET-VAN) in CH3OH and CH3OH/DCM media. Complex 1is discrete [(HgCl2)3LO-VAN], while 2is the coordination polymer (CP) [HgCl2LET-VAN]n. The complexes were characterized using spectroscopy, SCXRD, HRMS, PXRD, SEM-EDX, and XPS study. The X-ray structure revealed that 1crystallizes in the monoclinic space group P21/cand is built from isolated trinuclear units of [(HgCl2)3LO-VAN]. Similarly, 2crystallizes in the monoclinic space group P21/n, having polynuclear units of [HgCl2LET-VAN]n. The Hg(II) center has favorable stereochemical features and is five-coordinated, creating trigonal (1) and square bipyramidal geometries (2). DFT-D3 at the B3LYP/LanL2DZ level of theory using Gaussian 09 was used to explore the FMO/MEP/NBO and ELF-LOL plot of Hg complexes. Hirshfeld surface and 2D fingerprint plots were used to analyze the H···H, H···O/O···H, and H···Cl/Cl···H contacts. The FMO energy gap explains the complex’s conductivity and nanoelectronic applications. The transfer of electronic charge on the surface has been explained through NBO. ELF-LOL profile demonstrates exceptional complex stability. The existence of spodium bonding (SpBs)/σ-/π-holes and noncovalent interactions was investigated by DFT. The nature and strength of the Hg···Cl SpBs were analyzed by QTAIM and an NCI plot. The findings revealed that SpBs exhibit weak noncovalent interactions characterized by bond critical points (BCPs), bond paths, and reduced density gradient (RDG) iso-surfaces. The MEP surface demonstrated the presence of σ-/π-holes at the Hg atoms, facilitating directional SpB formation. Herein, the nature of the interaction energies is influenced by SpBs and the concurrent formation of additional noncovalent interactions such as π-stacking and CH···π, O contacts. Primarily, the research emphasizes the importance of σ-/π-hole interactions in forming mercury complexes through self-assembly.

Atrial fibrillation (AF) represents the most common arrhythmia in the postoperative setting. We aimed to investigate the incidence of postoperative AF (POAF) and determine its predictors, with a specific focus on inflammation markers. We performed a retrospective single tertiary center cohort study including consecutive adult patients who underwent a major surgical procedure between January 2016 and January 2020. Patients were divided into four subgroups according to the type of surgery. Among 53,387 included patients (79.4% male, age 64.5 ± 9.5 years), POAF occurred in 570 (1.1%) with a mean latency after surgery of 3.4 ± 2.6 days. Ninety patients died (0.17%) after a mean of 13.7 ± 8.4 days. The 28‐day arrhythmia‐free survival was lower in patients undergoing lung and cardiovascular surgery (p< .001). Patients who developed POAF had higher levels of C‐reactive protein (CRP) (0.70 ± 0.03 vs. 0.40 ± 0.01 log10 mg/dl; p< .001). In the multivariable Cox regression analysis, adjusting for confounding factors, CRP was an independent predictor of POAF [HR per 1 mg/dL increase in log‐scale = 1.81 (95% CI 1.18–2.79); p= .007]. Moreover, independent predictors of POAF were also age (HR/1 year increase = 1.06 (95% CI 1.04–1.08); I < .001), lung and cardiovascular surgery (HR 23.62; (95% CI 5.65–98.73); p< .001), and abdominal and esophageal surgery (HR 6.26; 95% CI 1.48–26.49; p= .013). Lung and cardiovascular surgery had the highest risk of POAF in the presented cohort. CRP was an independent predictor of POAF and postsurgery inflammation may represent a major driver in the pathophysiology of the arrhythmia. In the present study, POAF represents a frequent complication following several types of surgery (stratified into four groups) with a higher incidence after cardiac and thoracic surgery. In our casuistic inflammation (represented by CRP levels) is an independent predictor of POAF occurrence.

Positively charged ligands are scarce. Here, we report the synthesis of unprecedented cationic selenium-containing triazapentadiene ligand framework. The reaction between 2-pyridylselenyl reagents and NaN(CN)2in a 2:1 ratio produces the sodium complexes featuring the cationic selenium-containing triazapentadiene (SeTAP) ligand. The sodium-to-metal transmetalation allows facile preparation of SeTAP metal complexes, as exemplified by the reactions with CuCl2, AgNO3, NaAuCl4, and FeCl3. Density functional theory calculations have been used to analyze and characterize the chalcogen bonding interactions observed in the solid state for these compounds. Moreover, antifungal properties of the SeTAP ligand and its metal complexes were screened for in vitro activity against several phytopathogenic fungi. Phoma eupyrenaexhibited prominent sensitivity against the action of most of the tested compounds.

Four manganese(III) complexes, [MnL1Cl] (1), [MnL2Cl] (2), [Mn2(L2)2(N3)2] (3), and [Mn2(L1)2(NCS)2] (4){H2L1= N,N′-bis(5-chlorosalicylidene)-1,3-diaminopropane, H2L2= N,N′-bis(5-chlorosalicylidene)-2,2-dimethyl-1,3-diaminopropane} have been synthesized and characterized. The structures of the complexes were confirmed by single-crystal X-ray diffraction analysis. All four complexes showed a tendency to form supramolecular dimers in the solid state. Density functional theory (DFT) calculations have been used to investigate the supramolecular assemblies observed in the solid state of these complexes and to characterize the Mn···O interactions in terms of covalent/noncovalent nature and their importance for the formation of self-assembled dimers in complexes 1–4. QTAIM and NCIPlot calculations have been used to disclose the noncovalent nature of the Mn···O contacts in complexes 1–4, which can be considered as matere bonds (MaBs) instead of coordination bonds. Such a type of matere bond is unprecedented in square pyramidal Mn complexes. Energetically, the MaBs exhibit values ranging from −8 to −11 kcal/mol across these complexes. Therefore, this research highlights the attractive interactions between group 7 Mn(III) derivatives and Lewis bases involving a π-hole formed opposite one of the apical coordination bonds.

The capacity to selectively tune the optical and electrical properties of organic molecules has emerged as an effective strategy for the development of flexible optoelectrical devices. These physical properties are influenced by crystal packing, and as a result, they are expected to vary with polymorphic modifications. Herein, we illustrate the pivotal influence of polymorphism on the optoelectronic traits of the resulting solids, paving the way for prospective applications such as photosensitive Schottky devices. In this study, we isolated two distinct color polymorphs, denoted as Iand II, of a novel Schiff base, (E)-2-methoxy-4-methyl-6-((3-nitrophenyl)iminomethyl)phenol, obtained from the condensation reaction between 2-hydroxy-3-methoxy-5-methylbenzaldehyde and m-nitroaniline. These polymorphs Iand IIwere obtained in pure crystalline forms using different solvents, namely, acetonitrile and methanol, respectively. Analysis via X-ray crystallography unveiled that both forms Iand IIcrystallize within the orthorhombic unit cell, albeit with different space groups of P212121and Pca21, respectively. Notably, the nitro group in these polymorphic forms establishes distinct noncovalent interactions, ensuring the selective stability of each polymorphic form in the solid state with discernible contributions from the solvents. Furthermore, polymorphs Iand IIexhibited reversible thermochromic behaviors between room temperature and low temperature (77 K). Electrical conductivity and photosensitivity studies of the polymorphs revealed that the electrical properties of these polymorphs are significantly different, with notable enhancements observed, particularly for form II, upon illumination with visible light. Our results overall highlight the potential of polymorphic design as a promising avenue for fine-tuning the optoelectrical properties of organic crystalline materials, thereby opening avenues for their utilization in the fabrication of photosensitive devices.

The versatile coordination chemistry of (2Z,N’E)-N′-(4-oxothiazolidin-2-ylidene)picolinohydrazonamide (HAmDHotaz) facilitated the synthesis of new complexes with different silver(I) salts. This paper describes the synthesis and characterization, through elemental analysis and spectroscopic techniques (when solubility permits), of a series of compounds that illustrate the coordinative and structural diversity achievable with the HAmDHotaz ligand. Five silver clusters containing the [Ag8(AmDHotaz)4]4+nucleus were structurally analyzed by single-crystal X-ray diffraction and were found to exhibit solvomorphism. The compositions of these are [Ag8(AmDHotaz)4(NO3)3(MeOH)(H2O)](NO3)·MeOH·7.5H2O (1), {[Ag8(AmDHotaz)4(NO3)3(H2O)2](NO3)·9.5(H2O)}n(2), {[Ag8(AmDHotaz)4(NO3)3(H2O)2](NO3)·11.5(H2O)}n(2a), {[Ag8(AmDHotaz)4(NO3)2(H2O)2](NO3)(OH)·6H2O}n(3), and {[Ag8(AmDHotaz)4(NO3)2(H2O)](NO3)(OH)·4.5H2O}n(3a). Argentophilic interactions are present in each of the octanuclear structures, where Ag···Ag distances range from 2.828(2) to 2.986(1) Å. These distances are influenced by crystal packing, determined by the counterion and solvent molecules in the structure. In the solvatomorphs, solvent molecules were observed to be disordered. Various hydrogen-bonding interactions, such as N–H···O–N, O–H···O, N–H···O═C, C–H···O–N, and π–π stacking interactions, contribute to the crystal packing. The influence of these weak interactions on the crystal packing was further analyzed using DFT calculations and Bader’s theory of atoms-in-molecules, with a focus on argentophilic interactions and Ag···S interactions.

Through the interaction of a halogen bond donor (1,4-diiodotetrafluorobenzene; 1,4-FIB) with isomers of pyridyl-substituted nitronyl nitroxides (Py-NN), five novel cocrystals were constructed via halogen bonding. The cocrystals (pPy-NN)n·1,4-FIB (n= 1, 2, 4) and (mPy-NN)n·1,4-FIB (n= 1, 2) are represented by the discrete clusters Py-NN·1,4-FIB·NN-Py, cyclic tetrameric structures (pPy-NN)4·(1,4-FIB)4, or one-dimensional (1D) zigzag chains. Density functional theory calculations were used to analyze the nature of the halogen bonds and to compare the strengths of I···NPy and I···ONO interactions. The halogen bonds were shown to be quite strong, ranging from 6.4 to 9.0 kcal/mol, according to the QTAIM analysis. In addition, quantum chemical analyses revealed relatively weak exchange interactions of both ferromagnetic and antiferromagnetic nature, indicating a modulating effect of the halogen bonding on magnetic properties. These findings point to the potential usefulness of halogen bonding interactions for promoting the self-assembly of stable organic radicals for further use in the preparation of exchange-coupled organic spin systems.

Four Pt(II)(N^N^N) compounds featuring DMSO coordination at the fourth position were synthesized. Ligands varied in terms of pyridyl central ring (hydrogen/chlorine substituent) and lateral rings (triazoles with CF3substitution or tetrazoles). Coordination to pyridine yielded tetra-nitrogen coordinated Pt(II) complexes or Pt-functionalized polymers using commercial 4-pyridyl polyvinyl (PV) or dimethylaminopyridine. Luminescence behaviors exhibited remarkable environmental dependence. While some of the molecular compounds (tetrazole derivatives) in solid state displayed quenched luminescence, all the polymers exhibited 3MMLCT emission around 600 nm. Conversely, monomer emission was evident on poly(methyl methacrylate) or polystyrene matrices. DFT calculations were used to analyze the aggregation of the complexes both at the molecular level and coordinated to the PV polymer and their influence on the HOMO–LUMO gaps.

In parallel to the nature of the chalcogen atom (Ch) and nucleophile (Nu), the strength and directionality of chalcogen bonding (ChB) are also dependent on the electron donor or acceptor character of the functional group (R) at ∠R–Ch···Nu. Although Hammett’s para-substituent constant (σp) can be used for the quantitative description of substituent effects, herein, we found that due to participation of the substituents in various types of intermolecular interactions, there is no linear relationship between the σpof the substituent in R (X = −CH3, −H, −F, −Cl, −Br, and −NO2) and the experimental Se···N distance or ∠N–Se···N angle in 5-substituted benzo[c][1,2,5]selenadiazoles and their copper(II) complexes. Such a relationship is also not observed theoretically, which is rationalized by taking into consideration the formation of intramolecular hydrogen and chalcogen bonds in the Cu complexes. The chalcogen bonds have been analyzed using the quantum theory of “atoms in molecules” combined with the noncovalent interaction plot and energy decomposition analysis.

Two coordination complexes [Ni(Hpydco)2(bpy)] (1) and [Ni(pydco)(phen)(H2O)2]·4.5H2O 0.5CH3OH (2) have been synthesized using a mixed-ligand system including pyridine-2,5-dicarboxylic acid N-oxide (H2pydco) as an O-donor ligand and 2,2'-bipyridine (bpy) or 1,10-phenanthroline (phen) as a chelating N-donor ligand and NiCl2.6H2O as a source for Ni ions. The crystal structures of 1 and 2 form discrete complexes in which extensive π−π stacking interactions between aromatic rings of the N-donor ligands resulted in the formation of one dimensional (1D) chain-like structures. The chains are connected by hydrogen bonds to expand the structures into 2D-supramolecular networks. Hirshfeld surface analysis and Density Functional Theory(DFT) calculations were included to rationalize the relative strength of the π-stacking assemblies observed in both complexes.

Noncovalent interactions and the coordination bond-assisted capture of Pd(0) in supramolecular cavities of bis(2,4-bis(trichloromethyl)-1,3,5-triazapentadienato)-Pd(II) is reported. It was determined that the cooperation of a coordination bond and noncovalent interactions in the Pd(II)-mediated activation of a nitrile group at 2,2,2-trichloroacetonitrile or 2,2-dihaloacetonitrile in the presence of NH4OH or propan-2-one oxime in acetone, DMF, DMSO, or MeOH leads to various organic, supramolecular, and coordination compounds.

The design of the secondary coordination sphere of metal complexes has emerged as a powerful synthetic strategy in their application/function in catalysis, molecular recognition, and crystal engineering. In contrast to traditional approaches, herein, the secondary coordination sphere of copper(II) complexes was designed by using chalcogen (sulfur) bond donor auxiliary ligands (5-substituted-1,3,4-thiadiazol-2-amines) in one-pot activation of one nitrile group in an arylhydrazone ligand. The chalcogen bond donor ability of the auxiliary ligands markedly increases with the electron-withdrawing character of the substituents, as disclosed by X-ray diffraction and theoretical studies.

Progress with fluorescent flippers, small-molecule probes to image membrane tension in living systems, has been limited by the effort needed to synthesize the twisted push–pull mechanophore. Here, we move to a higher oxidation level to introduce a new design paradigm that allows the screening of flipper probes rapidly, at best in situ. Late-stage clicking of thioacetals and acetals allows simultaneous attachment of targeting units and interfacers and exploration of the critical chalcogen-bonding donor at the same time. Initial studies focus on plasma membrane targeting and develop the chemical space of acetals and thioacetals, from acyclic amino acids to cyclic 1,3-heterocycles covering dioxanes as well as dithiolanes, dithianes, and dithiepanes, derived also from classics in biology like cysteine, lipoic acid, asparagusic acid, DTT, and epidithiodiketopiperazines. From the functional point of view, the sensitivity of membrane tension imaging in living cells could be doubled, with lifetime differences in FLIM images increasing from 0.55 to 1.11 ns. From a theoretical point of view, the complexity of mechanically coupled chalcogen bonding is explored, revealing, among others, intriguing bifurcated chalcogen bonds.

The synthesis of fluorescein propargyl diether (L) and two different dinuclear gold(I) derivatives containing a water-soluble phosphane [1,3,5-triaza-7-phosphatricyclo[3.3.1.13.7]decane (PTA) for complex 1and 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane (DAPTA) for complex 2] has been successfully performed. All compounds display intrinsic emission from fluorescein, being less intense for gold(I) complexes due to the heavy-atom effect. All compounds aggregate in acetonitrile/water mixtures with the formation of larger aggregates for those samples containing more water content, as evidenced by dynamic light scattering and small-angle X-ray scattering experiments, in agreement with the absorption and emission data. The emission of the samples increases when they are used to obtain luminescent materials with four different organic matrices [poly(methyl methacrylate, polystyrene (PS), cellulose, and Zeonex]. The compounds display very high values of singlet oxygen (1O2) production in dichloromethane. Singlet oxygen production was also evaluated in the doped matrices, being the highest in PS and with an exciting increase on PS microspheres. Density functional theory (BP86-D3) and GFN2-xTB calculations were used to model the assembly of Land complexes 1and 2with the different organic matrices and rationalize the experimental findings based on the geometries, molecular electrostatic potential surfaces, and complementarity and HOMO–LUMO gaps.

Zn(II) (complex 1), Cd(II) (complex 2), and Hg(II) (complex 3) complexes have been synthesized using a triply protonated tptz (H3tptz3+) ligand and characterized mainly by single-crystal X-ray analysis. The general formula of all of the complexes is (H3tptz)3+·Cl–·[MCl4]2–·nH2O (where n= 1, 1.5, and 1.5 for complexes 1, 2, and 3, respectively). The crystallographic analysis reveals that the anion···π, anion···π+, and several hydrogen bonding interactions play a fundamental role in the stabilization of the self-assembled architectures that in turn help to enhance the dimensionality of all of the complexes. In addition, Hirshfeld surfaces and fingerprint plots have been deployed here to visualize the similarities and differences in hydrogen bonding interactions in 1–3, which are very important in forming supramolecular architectures. A density functional theory (DFT) study has been used to analyze and rationalize the supramolecular interactions by using molecular electrostatic potential (MEP) surfaces and combined QTAIM/NCI plots. Then, the device parameters for the complexes (1–3) have been thoroughly investigated by fabricating a Schottky barrier diode (SBD) on an indium tin oxide (ITO) substrate. It has been observed that the device made from complex 2is superior to those from complexes 1and 3, which has been explained in terms of band gaps, differences in the electronegativities of the central metal atoms, and the better supramolecular interactions involved. Finally, theoretical calculations have also been performed to analyze the experimental differences in band gaps as well as electrical conductivities observed for all of the complexes. Henceforth, the present work combined supramolecular, photophysical, and theoretical studies regarding group 12 metals in a single frame.

Cationic imidazoliumyl(phosphonio)-phosphanides [LC–P–PR3]+(1a–e+, LC= 4,5-dimethyl-1,3-diisopropylimidazolium-2-yl; R = alkyl, aryl) are obtained via the nucleophilic fragmentation of tetracationic tetraphosphetane [(LC–P)4][OTf]4(2[OTf]4) with tertiary phosphanes. They act as [LC–P]+transfer reagents in phospha-Wittig-type reactions, when converted with various thiocarbonyls, giving unprecedented cationic phosphaalkenes [LC–P═CR2]+(5a-f[OTf]) or phosphanides [LC–P–CR(NR2′)]+(6a-d[OTf]). Theoretical calculations suggest that three-membered cyclic thiophosphiranes are crucial intermediates of this reaction. To test this hypothesis, treatment of [LC–P–PPh3]+with phosphaalkenes, that are isolobal to thioketones, permits the isolation of diphosphirane salts 11a,b[OTf]. Furthermore, preliminary studies suggest that the cationic phosphaalkene [LC–P═CPh2]+may be employed to access rare examples of η2–P═C π-complexes with Pd0and Pt0when treated with [Pd(PPh3)4] and [Pt(PPh3)3] for which analogous complexes of neutral phosphaalkenes are scarce. The versatility of [LC–P]+as a valuable P1building block was showcased in substitution reactions of the transferred LC-substituent using nucleophiles. This is demonstrated through the reactions of 5a[OTf] and 6c[OTf] with Grignard reagents and KNPh2, providing a convenient, high-yielding access to MesP═CPh2(16) and otherwise difficult-to-synthesize 1,3-diphosphetane 17and P-aminophosphaalkenes.

In this study, we provide crystallographic (Protein Data Bank (PDB) inspection) and theoretical (RI-MP2/def2-TZVP//PBE0-D3/def2-SVP level of theory) evidence of the involvement of nucleobases in Regium−π bonds (RgBs). This noncovalent interaction involves an electrophilic site located on an element of group 11 (Cu, Ag, and Au) and an electron-rich species (lone pair, LP donor, or π-system). Concretely, an initial PDB search revealed several examples where RgBs were undertaken involving DNA bases and Cu(II), Ag(I), and Au(I/III) ions. While coordination positions (mainly at the N atoms of the base) are well known, the noncovalent binding force between these counterparts has been scarcely studied in the literature. In this regard, computational models shed light on the strength and directionality properties of the interaction, which was also further characterized from a charge-density perspective using Bader’s “atoms in molecules” (AIM) theory, noncovalent interaction plot (NCIplot) visual index, and natural bonding orbital (NBO) analyses. As far as our knowledge extends, this is the first time that RgBs in metal–DNA complexes are systematically analyzed, and we believe the results might be useful for scientists working in the field of nucleic acid engineering and chemical biology as well as to increase the visibility of the interaction among the biological community.

The autocatalysis of epoxide-opening ether cyclizations on the aromatic surface of anion−π catalysts stands out as a leading example of emergent properties expected from the integration of unorthodox interactions into catalysis. A working hypothesis was proposed early on, but the mechanism of anion−π autocatalysis has never been elucidated. Here, we show that anion−π autocatalysis is almost independent of peripheral crowding in substrate and product. Inaccessible asymmetric anion−π autocatalysis and sometimes erratic reproducibility further support that the origin of anion−π autocatalysis is more complex than originally assumed. The apparent long-distance communication without physical contact calls for the inclusion of water between substrate and product on the catalytic aromatic surface. Efficient anion−π autocatalysis around equimolar amounts but poor activity in dry solvents and with excess water indicate that this inclusion of water requires high precision. Computational models suggest that two water molecules transmit dual substrate activation by the product and serve as proton shuttles along antiparallel but decoupled hydrogen-bonded chains to delocalize and stabilize evolving charge density in the transition state by “anion−π double bonds”. This new transition-state model of anion−π autocatalysis provides a plausible mechanism that explains experimental results and brings anion−π catalysis to an unprecedented level of sophistication.

Five new copper(I) complexes─composed of the paired dibenzohalolium and [CuL2]−(L = 1,2,4-oxadiazolate) counterions in which O,O-atoms of the anion are simultaneously linked to the halogen atom─were generated and isolated as the solid via the three-component reaction between [Cu(MeCN)4](BF4), sodium 1,2,4-oxadiazolates, and dibenzohalolium triflates (or trifluoroacetates). This reaction is different from the previously reported CuI-catalyzed arylation of 1,2,4-oxadiazolones by diaryliodonium salts. Inspection of the solid-state X-ray structures of the complexes revealed the strong three-center X···O,O (X = Br, I) halogen bonding occurred between the oxadiazolate moieties and dibenzohalolium cation. According to performed theoretical calculations, this noncovalent interaction (or noncovalent chelation) was recognized as the main force in the stabilization of the copper(I) complexes. An explanation for the different behavior of complexes, which provide either chelate or nonchelate binding, is based on the occurrence of additional −CH3···π interactions, which were also quantified.

The simultaneous binding of a molecular entity through two interactions is a frequently pursued recognition mode due to the advantages it offers in securing molecular self-assembly. Here, we report how the planarity of the benzothienoiodolium (BTI) cation allows for preorganizing in the cation plane the hydrogen, halogen, and chalcogen bonds (HBs, XBs, and ChBs, respectively) formed by the phenyl hydrogen, iodolium iodine, and thienyl sulfur. Crystallographic analyses of some BTI salts show how this interaction coplanarity enables their coupling to point toward a single anion that is coordinated via the supramolecular and heteroditopic synthon XB/HB or XB/ChB, the latter observed here for the first time. These synthons adopt a Janus-like arrangement around iodine. Crystallographic information suggests that interactions of the synthons act synergistically, e.g., when resulting in the unusually short ChBs formed by the thienyl sulfur. Determination of the molecular electrostatic potential, Bader’s quantum theory of “atoms-in-molecules” analysis, and natural bond orbital investigations give information on the nature and energetic aspects of the short contacts observed in crystals.

The importance of tetrel bonds (TtBs) in spontaneous self-assembly has been highlighted in two new lead(II) complexes: i.e. Pb[S2P{OC6H4(4-C(CH3)3)}2]2(1) and Pb[S2P{OC6H4(4-C2H5)}2]2(2), which were successfully isolated and characterized by FT-IR, UV–vis and multinuclear NMR (31P, 1H and 13C) spectroscopy. The structures of both complexes have been confirmed by single-crystal X-ray diffraction analyses. Interestingly, lead is coordinated by three sulfur atoms in 1but by four sulfur atoms in 2, due to stereochemically active lone pair electrons, thus leading to trigonal-pyramidal and tetragonal-pyramidal geometries, respectively. Complex 1is the first example of a lead(II) dithiophosphate wherein the lead(II) center is coordinated to three S atoms. These complexes are stabilized at a lower coordination number and display hemidirected structures that allow forming σ-hole bonds. The lead(II) center establishes short contacts with sulfur atoms to form Pb···S TtBs that contribute to the construction of a self-assembled dimer in 1but to a supramolecular polymer in 2. The supramolecular assemblies are further stabilized by Pb···π TtB interactions. The attractive nature of TtBs has been studied by DFT calculations and characterized using a combination of Bader’s quantum theory of atoms-in-molecules (QTAIM) and noncovalent interaction plot (NCI plot) index based on a reduced density gradient (NCI-RDG) analysis. A systematic Hirshfeld surface analysis facilitates a comparison of intermolecular interactions such as C–H···π, π···π, Pb···S, and Pb···π in both complexes, which play a crucial role in the crystal engineering.

A novel [3+2] cycloaddition reaction between 2-pyridylselenyl halides or trifluoroacetates and isocyanates is described herein. This new convenient methodology allows the synthesis of novel 3-oxo-1,2,4-selenodiazolium scaffolds, which are inaccessible by the known methods. The coupling proceeds efficiently for a broad scope of substrates under mild conditions and allows preparation of cationic 3-oxo-1,2,4-selenodiazolium salts in high yields. The mechanism was analyzed using DFT calculations, evidencing the concerted nature of the novel cycloaddition reaction. The new Se-containing heterocycles were demonstrated to be structurally easily tunable donors of the chalcogen bonding (ChB). Noncovalent interactions in the solid state were studied using DFT calculations, molecular electrostatic potential surfaces and the quantum theory of atoms-in-molecules.

The application of halogen bonding in pharmaceutical chemistry remains a challenge. In this work, novel halogen-bonded cocrystals based on azole antifungal active pharmaceutical ingredients (APIs) and the ditopic molecule 1,4-diiodotetrafluorobenzene are reported. Their crystal structural features, spectroscopic properties, and thermal stability were studied. The components are bound through I···N from the triazole moieties present in all of the compounds. The molecular electrostatic potential (MEP) surfaces and quantum theory of atoms in molecules (QTAIM) calculations are used to rationalize the presence of hydrogen and halogen bonds in the resulting structures and their energetic analysis. The relative halogen bond ability of the different groups of voriconazole, fluconazole, and itraconazole was analyzed using MEP surfaces, demonstrating this approach to be an interesting tool to predict halogen-bonding preferences.

C(sp3) atoms are known to act as electrophilic sites in self-assembly processes, and in all cases reported till now, they form only one interaction with nucleophiles; that is, they function as monodentate tetrel bond donors. This manuscript reports experimental (X-ray structural analysis) and theoretical evidence (DFT calculations), proving that the methylene carbon in bis-pyridinium methylene salts establishes two short and directional C(sp3)···anion interactions; that is, they function as bidentate tetrel bond donors.

In the setting of structural heart disease, ventricular tachycardia (VT) is typically associated with a re-entrant mechanism. In patients with hemodynamically tolerated VTs, activation and entrainment mapping remain the gold standard for the identification of the critical parts of the circuit. However, this is rarely accomplished, as most VTs are not hemodynamically tolerated to permit mapping during tachycardia. Other limitations include noninducibility of arrhythmia or nonsustained VT. This has led to the development of substrate mapping techniques during sinus rhythm, eliminating the need for prolonged periods of mapping during tachycardia. Recurrence rates following VT ablation are high; therefore, new mapping techniques for substrate characterization are required. Advances in catheter technology and especially multielectrode mapping of abnormal electrograms has increased the ability to identify the mechanism of scar-related VT. Several substrate-guided approaches have been developed to overcome this, including scar homogenization and late potential mapping. Dynamic substrate changes are mainly identified within regions of myocardial scar and can be identified as local abnormal ventricular activities. Furthermore, mapping strategies incorporating ventricular extrastimulation, including from different directions and coupling intervals, have been shown to increase the accuracy of substrate mapping. The implementation of extrastimulus substrate mapping and automated annotation require less extensive ablation and would make VT ablation procedures less cumbersome and accessible to more patients.

A typical halogen bond (HaB) donor, 1,4-dibromo-2,3,5,6-tetrafluorobenzene (FBB), was cocrystallized with the isocyanide CNMes and the cyanide NCMes to give two isostructural cocrystals, (CNMes)·FBB and (NCMes)·FBB. Their solid-state architecture exhibits a close similarity between the isocyanide and cyanide groups in their HaB-accepting role. This similarity and particular bonding features of the HaBs were additionally verified by theoretical calculations (molecular electrostatic potential analysis, electron density/electrostatic potential profiles, atoms-in-molecules charge analysis, and calculations of pKavalues and binding energies). Remarkably, both cocrystals form unusual heterohexamers where one Br atom of FBB simultaneously forms four contacts with two C (or N) and two Br atoms of neighboring molecules. On the basis of the geometric parameters and the theoretical data, these contacts can be defined as five-center tetrafurcated μ4-Br···(C, Br, C, Br) and μ4-Br···(N, Br, N, Br) HaBs; this is the first observation of the tetrafurcated HaB involving four disunited HaB acceptors.

The two isostructural one-dimensional coordination polymers (1D CPs) [Cu(5-nip)(3-Clpy)2]n(1) and [Cu(5-nip)(3-Brpy)2]n(2) have been synthesized using a 5-nitroisophthalic acid (H25-nip) linker and the meta-substituted 3-chloropyridine (3-Clpy)/3-bromopyridine (3-Brpy) auxiliary ligands. The structural architectures and supramolecular interactions of the CPs have been investigated by single-crystal X-ray diffraction (SCXRD) and density functional theory (DFT) studies, respectively. The SCXRD study reveals that CPs 1and 2form a 1D double-chain structure with carboxylato-bridged cyclic secondary building units (SBUs). Interestingly, both CPs involve type I halogen···halogen (X···X) interactions combined with π···π stacking interactions to generate a three-dimensional (3D) supramolecular network. Moreover, both CPs exhibit interesting X···N π-hole interactions involving a nitro group as the electron acceptor. Both CPs show electrical conductivity in the semiconducting regime and behave as Schottky diodes. However, CP 1has a higher electrical conductivity in comparison to CP 2.

This study aimed to evaluate the progression of electrophysiological phenomena in a cohort of patients with paroxysmal atrial fibrillation (PAF) and persistent atrial fibrillation (PsAF).

The main feedstock for the value-added phosphorus chemicals used in industry and research is white phosphorus (P4), from which the key intermediate for forming P(III) compounds is PCl3. Owing to its high reactivity, syntheses based on PCl3are often accompanied by product mixtures and laborious work-up procedures, so an alternative process to form a viable P(III) transfer reagent is desirable. Our concept of oxidative onioation, where white phosphorus is selectively converted into triflate salts of versatile P1transfer reagents such as [P(LN)3][OTf]3(LNis a cationic, N-based substituent; that is, 4-dimethylaminopyridinio), provides a convenient alternative for the implementation of P–O, P–N and P–C bonds while circumventing the use of PCl3. We use p-block element compounds of type RnE (for example, Ph3As or PhI) to access weak adducts between nitrogen Lewis bases LNand the corresponding dications [RnELN]2+. The proposed equilibrium between [RnELN]2++ LNand [RnE(LN)2]2+allows for the complete oxidative onioation of all six P–P bonds in P4to yield highly reactive and versatile trications [P(LN)3]3+.

Temporary pacing is necessary in pacemaker‐dependent patients after transvenous lead extraction (TLE) for cardiac implantable electronic device infection. In case of unavailability of other accesses, we propose to use the ipsilateral subclavian access (ISA) combined with a standard permanent active fixation lead for the temporary pacemaker and present preliminary data. We consecutively enrolled patients undergoing TLE who received a temporary pacemaker using the ISA between August 2016 and April 2020 at our centre. During the observation period, 36 patients undergoing TLE for pocket infection (72.2%), endocarditis (25.0%) or other causes received a temporary pacemaker over the ISA. Their mean age was 77.0 ± 10.7 years, and 13.9% were female. Complete TLE was achieved in 94.4%. There were no major periprocedural complications. Intra‐hospital mortality was 11.1%. Pocket revision was performed in 19.4%. During long‐term follow‐up (23 ± 13 months), 8.3% had a relapse of local pocket infection and 2.8% needed rehospitalization for reintervention. Temporary pacing using a standard permanent active fixation lead using the ISA is a convenient alternative to conventional venous accesses. However, risks of implanting a lead into a previously infected area have to be taken into account. We propose to use the ipsilateral subclavian access (ISA) for temporary pacing in selected pacemaker‐dependent patients undergoing transvenous lead extraction (TLE). We show a low complication rate in a retrospective single‐centre study of 36 consecutive patients using the ISA after TLE. Use of the ISA may be restricted to selected patients as there is a risk of infection recurrence.

A photoactive two-dimensional metal–organic framework (2D MOF) [Zn(4-spy)(DCTP)]n(1) [where 4-spy = 4-styrylpyridine and H2DCTP = 2,5-dichloroterephthalic acid] undergoes photochemical [2 + 2] cycloaddition on UV irradiation to obtain three-dimensional (3D) MOF [Zn(rctt-4-ppcb)(DCTP)]n(2) [rctt-4-ppcb = 1,3-bis(4′-pyridyl)-2,4-bis(phenyl)cyclobutane] in a single-crystal to single-crystal (SCSC) manner. This structural transformation leads to stronger halogen···halogen interaction that is well-corroborated by density functional theory (DFT) calculations.

The work represents a rare example of an aza-crown-based macrocyclic chemosensor, H2DTC(H2DTC= 1,16-dihydroxy-tetraaza-30-crown-8) for the selective detection of both Zn2+and Cu2+in HEPES buffer medium (pH 7.4). H2DTCexhibits a fluorescence response for both Zn2+and Cu2+ions. The reversibility of the chemosensor in its binding with Zn2+and Cu2+ions is also examined using a Na2EDTA solution. H2DTCexhibits a chelation-enhanced fluorescence (CHEF) effect in the presence of Zn2+ions and a quenching effect (CHEQ) in the presence of paramagnetic Cu2+ions. Furthermore, the geometry and spectral properties of H2DTCand the chemosensor bound to Zn2+have been studied by DFT and TDDFT calculations. The limit of detection (LOD) values are 0.11 × 10–9and 0.27 × 10–9M for Cu2+and Zn2+, respectively. The formation constants for the Zn2+and Cu2+complexes have been measured by pH-potentiometry in 0.15 M NaCl in 70:30 (v:v) water:ethanol at 298.1 K. UV–vis absorption and fluorometric spectral data and pH-potentiometric titrations indicate 1:1 and 2:1 metal:chemosensor species. In the solid state H2DTCis able to accommodate up to four metal ions, as proved by the crystal structures of the complexes [Zn4(DTC)(OH)2(NO3)4] (1) and {[Cu4(DTC)(OCH3)2(NO3)4]·H2O}n(2). H2DTCcan be used as a potential chemosensor for monitoring Zn2+and Cu2+ions in biological and environmental media with outstanding accuracy and precision. The propensity of H2DTCto detect intracellular Cu2+and Zn2+ions in the triple negative human breast cancer cell line MDA-MB-468 and in HeLa cells has been determined by fluorescence cell imaging.

The crystal structures of two new polymorphs of the 1/1 pterostilbene/picolinic acid cocrystal have been analyzed by single-crystal X-ray diffraction and studied by means of DFT calculations and a set of computational tools (QTAIM, NCIplot, MEP). The observation of a new R22(10) synthon in each of the two polymorphs has been analyzed energetically, characterized using the topology of the electron density, and rationalized using the MEP surfaces. The exceptional bioavailability of the cocrystal is explained on the basis of BFDH morphology calculations, and the study is complemented by a deep analysis of the supramolecular synthons formed by both neutral and zwitterionic forms of picolinic acid, a versatile coformer for crystal engineering.

In this study, we provide experimental (Protein Data Bank (PDB) inspection) and theoretical (RI-MP2/def2-TZVP level of theory) evidence of the involvement of charge assisted chalcogen bonding (ChB) interactions in the recognition and folding mechanisms of S-adenosylmethionine (SAM) riboswitches. Concretely, an initial PDB search revealed several examples where ChBs between S-adenosyl methionine (SAM)/adenosyl selenomethionine (EEM) molecules and uracil (U) bases belonging to RNA take place. While these interactions are usually described as a merely Coulombic attraction between the positively charged S/Se group and RNA, theoretical calculations indicated that the σ holes of S and Se are involved. Moreover, computational models shed light on the strength and directionality properties of the interaction, which was also further characterized from a charge-density perspective using Bader’s “Atoms in Molecules” (AIM) theory, Non-Covalent Interaction plot (NCIplot) visual index, and Natural Bonding Orbital (NBO) analyses. As far as our knowledge extends, this is the first time that ChBs in SAM–RNA complexes have been systematically analyzed, and we believe the results might be useful for scientists working in the field of RNA engineering and chemical biology as well as to increase the visibility of the interaction among the biological community.

Understanding the structural and functional implications of metal ions is of pivotal significance to chemical biology. Herein, we report first time the evidence of spodium bonds (SpB’s, an attractive noncovalent force involving elements from group 12 and electron-rich species) in tetrahedral Zn-binding sites. Through a combined crystallographic (PDB analysis) and computational (ab initiocalculations) study, we demonstrate that Zn SpB’s are abundant and might be involved in protein structure and enzyme inhibition.

The diketonate complex [Cu{OC(tBu)CC(H)O}2] (1) and its cocrystals with 1,4-diiodotetrafluorobenzene (1,4-FIB), 1,3,5-triiodotrifluorobenzene (1,3,5-FIB), and 1,4-dioxane were studied by X-ray diffraction. In the solid state, 1exhibits the cis-geometry with syn-tBu groups; the geometry is stable in storage at 20–25 °C or even in heating in the solid state, solutions, or sublimation. The DFT modeling for isolated molecules of cis- and trans-1revealed that the cis-form is only slightly more energetically favorable. However, cocrystals trans-1·C4H8O2, trans-1·1,4-FIB, and trans-1·1,3,5-FIB·C4H8O2display the trans-geometry with the anti-tBu substituents; the comparison of the geometries revealed the facile crystal-packing-driven cis-to-transisomerization of 1upon the cocrystal growth. Compared to the cocrystals of the unsubstituted [Cu(acetylacetonate)2] complex with the FIBs, in the assembled architectures of trans-1·1,4-FIB and trans-1·1,3,5-FIB·C4H8O2, the switch from the bridging (μ2-I)···O,O to two-center I···O halogen bonding is demonstrated. The theoretical study revealed that the energetic features of the (μ2-I)···O,O halogen bonding in [Cu(acetylacetonate)2]·1,4-FIB are similar to those of the I···O halogen bonding in 1·1,4-FIB. Variable-temperature XRD data (at 100, 150, 200, 250, and 300 K) for cis-1and trans-1·1,4-FIB indicate that the infinite chains of molecules stabilized by I···O halogen bonding remain the main packing motif at all applied temperatures.

The work herein describes the synthesis of five three-coordinate silver(I) complexes comprising a bidentate ligand L1, either bpy (2,2′-bipyridyl) or bpyMe2(4,4′-dimethyl-2,2′-dipyridyl), and a monodentate ligand L2, either mtz (1-methyl-1H-1,2,3-triazole), 4-Etpy (4-ethylpyridine), or 4-DMAP (N,N-dimethylpyridin-4-amine). Upon reaction of the three-coordinate silver(I) complexes with 0.5 equiv of I2, the reactions quantitatively produce a 1:1 pair of complexes of a four-coordinate silver(I) complex [Ag(L1)2]PF6and a two-coordinate iodonium complex [I(L2)2]PF6. The combination of [Ag(bpyMe2)2]PF6and [I(4-DMAP)2]PF6gave rise to an I+···Ag+interaction where the I+acts as a nucleophile, only the second example of which, that was observed in both the solution (NMR) and solid (X-ray) states.

The complexes [RhX(COD)]2(X = Cl, Br; COD = 1,5-cyclooctadiene) form cocrystals with s-hole iodine donors. X-ray diffraction studies and extensive theoretical considerations indicate that the dz2-orbitals of two positively charged rhodium(I) centers provide sufficient nucleophilicity to form a three-center halogen bond (XB) with the s-hole donors. The two metal centers function as an integrated XB acceptor, providing assembly via a metal-involving XB.

Cocrystallization of the nitrosoguanidinate complexes [Ni{NH═C(NR2)NN(O)}2] (R2= Me2(1), Me/Ph (2), C5H10(3)) with 1,2-diiodotetrafluorobenzene (1,2-FIB), 1,4-diiodotetrafluorobenzene (1,4-FIB), 1,3,5-triiodotrifluorobenzene (1,3,5-FIB), and tetraiodoethylene (C2I4) gave new cocrystals (1–3)·2(1,2-FIB), 2·(1,4-FIB), 3·2(1,3,5-FIB), 1·C2I4, and 2·2C2I4; all of these solids were studied by single-crystal X-ray diffraction. Each structure exhibits the asymmetric bifurcated halogen bond μ2-I···(N,O) as a characteristic feature and a structure-directing contact. DFT calculations were used to evaluate the energetic features of the bifurcated halogen bonds that range from −6.7 to −8.3 kcal/mol; in general, the I···O contact is stronger that the I···N contact. Molecular electrostatic potential (MEP) surfaces along with the quantum theory of “atoms in molecules” (QTAIM) and the noncovalent interaction plot index (NCIPlot) computational tools were used to characterize the bifurcated halogen bonds in the cocrystals of 1–3. Various types of bifurcated halogen bonds involving nonmetal atoms as halogen-bond-accepting centers were systematized and categorized.

In this work we report structural and computational studies of favipiravir, which is now used as a drug for COVID-19 treatment. The molecule is completely flat and stabilized by an intramolecular O–H···O hydrogen bond, yielding a six-membered pseudo-aromatic ring. The aromaticity index of this pseudo-aromatic ring was found to be 0.748, while the same indix for the pyrazine ring in favipiravir was found to be 0.954. The crystal packing of favipiravir is mainly constructed through intermolecular N–H···O, N–H···N and C–H···O hydrogen bonds, yielding a 3D supramolecular framework with a zsttopology defined by the point symbol of (65·8). The crystal structure of favipiravir is further stabilized by weak C–F···F–C intermolecular type II dihalogen interactions, yielding a 1D supramolecular polymeric chain. More than 80% of the total Hirshfeld surface area for favipiravir is occupied by H···H/C/N/O/F and C···N/O contacts. Energy frameworks have been calculated to additionally analyze the overall crystal packing. It was established that the structure of favipiravir is mainly characterized by the dispersion energy framework followed by the less significant electrostatic energy framework contribution. Finally, by using density functional theory (DFT) calculations and the quantum theory of atoms in molecules, we have assigned the interaction energy of each hydrogen bond, which can be helpful to develop scoring functions to be used in force fields/docking calculations.

Four new heterometallic Cu(II)–U(VI) species, [{(CuL1)(CH3CN)}UO2(NO3)2] (1), [{(CuL2)(CH3CN)}UO2(NO3)2] (2), [{(CuL3)(H2O)}UO2(NO3)2] (3), and [UO2(NO3)2(H2O)2]·2[CuL4]·H2O (4), were synthesized using four different metalloligands ([CuL1], [CuL2], [CuL3], and [CuL4], respectively) derived from four unsymmetrically dicondensed N,O-donor Schiff bases. Single-crystal structural analyses revealed that complexes 1, 2, and 3have a discrete dinuclear [Cu–UO2] core in which one metalloligand, [CuL], is connected to the uranyl moiety via a double phenoxido bridge. Two chelating nitrate ions complete the octa-coordination around uranium. Species 4is a cocrystal, where a uranyl nitrate dihydrate is sandwiched between two metalloligands [CuL4] by the formation of strong hydrogen bonds between the H atoms of the coordinated water molecules to U(VI) and the O atoms of [CuL4]. Spectrophotometric titrations of these four metalloligands with uranyl nitrate dihydrate in acetonitrile showed a well-anchored isosbestic point between 300 and 500 nm in all cases, conforming with the coordination of [CuL1], [CuL2], [CuL3], and the H-bonding interaction of [CuL4] with UO2(NO3)2. This behavior of [CuL4] was utilized to selectively bind metal ions (e.g., Mg2+, Ca2+, Sr2+, Ba2+, and La3+) in the presence of UO2(NO3)2·2H2O in acetonitrile. The formation of these Cu(II)–U(VI) species in solution was also evaluated by steady-state fluorescence quenching experiments. The difference in the coordination behavior of these metalloligands toward [UO2(NO3)2(H2O)2] was studied by density functional theory calculations. The lower flexibility of the ethylenediamine ring and a large negative binding energy obtained from the evaluation of H bonds and supramolecular interactions between [CuL4] and [UO2(NO3)2(H2O)2] corroborate the formation of cocrystal 4. A very good linear correlation (r2= 0.9949) was observed between the experimental U═O stretching frequencies and the strength of the equatorial bonds that connect the U atom to the metalloligand.

A new cocrystal formed between the nutraceutical compounds pterostilbene and theophylline was synthesized and X-ray characterized in the form of a dichloromethane solvate. An interesting supramolecular assembly is formed by means of a combination of common and uncomment π–π and H-bonding interactions. It was computationally studied by a combination of density functional theory (DFT), quantum theory of “atoms-in-molecules”, and noncovalent interaction plot approaches, and the analyses revealed a π(C═C)···H-bond array interaction, which is the first description of this type of interaction where the donor π-system is a double bond. The participation of the cocrystallized CH2Cl2solvent molecule in Cl···Cl and C–H···π interactions was also studied using DFT and Hirshfeld surface calculations. The Cambridge structural database was inspected to investigate whether the π···H-bond array interaction is common in other theophylline cocrystals. Other examples where the π-system of an aromatic ring or an amido group interact with the H-bond array were found in literature and further discussed herein.

The complex [Ni(S2COEt)2] (1) and 1,4-diiodotertafluorobenzene (1,4-FIB) or 1,3,5-triiodotrifluorobenzene (1,3,5-FIB) were cocrystallized to form solid adducts 1·2(1,4-FIB) and 1·2(1,3,5-FIB), respectively; the structures of the adducts were studied by X-ray crystallography. The introduction of any one of the FIBs dramatically changed the supramolecular architecture of 1, and the structure-directing interactions changed from predominantly Ni···S semicoordination (in 1) to I···S halogen bonding between an FIB and the electron-donating S atoms of 1(in the adducts). The semicoordination bond breaking and halogen bond making upon the interaction of 1with the FIBs make the employed crystal engineering approach relevant (or even similar) to the molecular synthesis of metal species. The DFT study indicates that the strength of both types of interactions in the adducts are comparable (−3.0 to −4.9 kcal/mol and −4.3 to −4.9 kcal/mol) but very different in regard to their physical nature. If the electrostatics determine the I···S halogen bonds, the Ni···S semicoordination bonding is basically dominated by orbital effects.

Perfluorinated arenes (benzeneFderivatives, diphenylF, naphthaleneF) were converted into X-perfluoroarenes (X = Br, I) via the developed one-pot protocol based on [Fe(acetylacetonate)3]-assisted C–F functionalization. The syntheses proceed under mild conditions and employ readily available perfluorinated arenes, which are treated with EtMgBr followed by addition of X2/[Fe(acetylacetonate)3] (0.8 mol %); yields range from good to moderate. The σ-hole donor properties of the obtained mono- and di-X-perfluoroarenes and the significance of these species for halogen-bonding-based crystal engineering was illustrated in a series of postsynthetic experiments, all supported by density functional theory (DFT) energy calculations, molecular electrostatic potential (MEP) surface analysis, and the quantum theory of atoms in molecules (QTAIM). These include (i) a solid-state X-ray diffraction study of X-perfluoroarene self-association (dimerization) via iodine σ-hole—electron belt interactions (three X-ray structures) and (ii) verification of X-perfluoroarene σ-hole donor abilities by their interactions with iodides acting as external σ-hole acceptors (five X-ray structures); a Hirshfeld surface analysis was performed for all eight structures.

In this study, we report experimental (Protein Data Bank (PDB) search) and theoretical (RI-MP2/def2-TZVP level of theory) evidence of the nature, stability, and directionality properties of intramolecular halogen bonding interactions (HaBs) between 5-bromo/5-iodoracil bases and backbone phosphate groups in nucleic acids (NAs). A PDB survey revealed relevant examples where intramolecular HaBs are undertaken and serve as a structural source of stability in RNA and DNA molecules. In order to develop suitable energy predictors, we started this investigation by calculating the interaction energy values and both the potential V(r) and kinetic G(r) energy densities (using Bader’s “atoms in molecules” theory) of several halogen bond complexes involving 5-bromo/5-iodoracil molecules and biologically relevant electron donors. Once the energy predictors based on V(r)/G(r) energy densities were developed, we analyzed the HaBs observed in the biological examples retrieved from the PDB search in order to estimate the strength of the interaction. As far as our knowledge extends, intramolecular halogen bonds in NAs have not been previously quantified in the literature using this methodology and may be of great importance in understanding their structural properties as well as in the construction of molecular materials with DNA and other biological macromolecules.