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The synthesis and characterization of five metal complexes derived from sodium meclofenamate (1) are reported: [Cd(C14H10NO2Cl2)2·(CH3OH)]n·nCH3OH (6), [Pb(C14H10NO2Cl2)2]n (7), [Co(C14H10NO2Cl2)]n (8), [Cu(C14H10NO2Cl2)]n (9), and [Cu(C14H10NO2Cl2)2(C5H5N)2] (10) (C14H10NO2Cl2=meclofenamate; C5H5N=pyridine). The characterization of the compounds was based on FTIR and UV-visible spectroscopy, mass spectrometry and, in the case of complexes 6 and 10, single crystal X-ray diffraction analysis. For compound 6, the structural analysis revealed a 1-D polymeric chain structure, in which pentagonal planar [Cd(RCOO)2(CH3OH)] units were linked through bridging carboxylate functions of the meclofenamate ligands. The overall coordination environment of the Cd(II) ions was seven-coordinate, since each carboxylate group exhibited a µ3-bridging coordination mode. On the other hand, for complex 10 a discrete mononuclear structure was observed, in which the six-coordinate copper(II) metal atoms were coordinated by two pyridine molecules and the carboxylate functions of two meclofenamate entities, in an anisobidentate coordination mode. The antibacterial activity of compounds 6-9 against four strains of Gram positive (Staphylococcus aureus and Bacillus subtilis) and Gram negative (Escherichia coli and Pseudomonas aeruginosa) bacteria was examined, finding that only complex 6 was active. Additionally, it was found that the Co(II) and Cu(II) complexes 8 and 9 showed peroxidase activity. [ABSTRACT FROM AUTHOR]

The solid state photodimerization of ethyl coumarin-3-carboxylate and its 6-Cl and 6-Br (1a-c) derivatives as well as the methyl and ethyl alcoholysis derivatives of ethyl coumarin-3-carboxylate photodimer are reported in the context of crystal engineering. Ethyl coumarin-3-carboxylates photodimerize topochemically to form anti head-to-tail stereoisomers (2a-c). The extent of lactone methanolysis of 2a depends on the boiling temperature of the solvent to produce 2-(2-hydroxyphenyl)-3-oxo-8bH-4-oxa-cyclobuta[a]naphthalene-1,1,2a-tricarboxylic acid 1,2a-diethyl ester 1-methyl ester (3a) and 2,4-bis-[(2-hydroxyphenyl]cyclobutane-1,1,3,3-tetracarboxylic acid diethyl ester dimethyl ester (4a) in 1:2 proportion, whereas the ethanolysis of 2a only yields 2-(2-hydroxyphenyl)-3-oxo-8bH-4-oxa-cyclobuta[a]naphthalene-1,1,2a-tricarboxylic acid triethyl ester (5a). The molecular structure of 2a-c and 3-5a were elucidated by 1H and 13C NMR spectroscopy. Also the molecular and supramolecular structures of 2a,b and 3,4a were studied by X-ray diffraction. Most of the C-H...X (X = O, Ph), π...π and dipolar interactions in the photodimers 2a,b and derivative 3a are preserved from the corresponding original coumarin monomers. Thus the supramolecular structure of ethyl coumarin-3-carboxylate is conserved through this group of compounds as if they would have a "supramolecular memory". [image omitted] [ABSTRACT FROM AUTHOR]

Nine tetraalkylammonium salts, with R = Me, Et, nPr and nBu, of four different carboxylic acids, namely isophthalic acid, 5-nitroisophthalic acid, trimesic acid and pyromellitic acid (1,2,4,5-benzenetetracarboxylic acid), have been prepared and their supramolecular structures analyzed by X-ray crystallography. The [RCOOH...HOOCR] homodimeric motif characteristic for carboxylic acids has not been detected, but instead, in all compounds a [RCOOH...OOCR]- unit was present. The hydrogen-bonding geometries and interaction energies of the different discrete and water-expanded hydrogen-bonding patterns formed between the carboxyl and the carboxylate group have been analyzed systematically by theoretical calculations at the MP2/6-31G(d,p) level of theory. Carboxylates are promising candidates for crystal engineering and [O-H...O]- interactions play an important role for the structural organization and chemistry of biomolecules. [image omitted] [ABSTRACT FROM AUTHOR]

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Boroxine- and borazine-cage analogs to C 20 , C 60 , and C 70 were calculated and compared in terms of structure, strain indicators, and physical properties relevant to nanoscale applications. The results show C 60 and C 70 type cages are less strained than the smaller congener, primarily due to minimized bending in the B-arylene-B segments. The smallest cage calculated has a diameter of 2.4 nm, which increases up to 4.9 nm by either variation of the polyhedron (C 20 < C 60 < C 70 -type cage) or organic spacer elongation between boron centers. All calculated cages are porous (apertures ranging from 0.6 to 1.9 nm). Molecular electrostatic potential and Hirshfeld population analysis revealed both nucleophilic and electrophilic sites in the interior and exterior cage surfaces. HOMO-LUMO gaps range from 3.98 to 4.89 eV and 5.10-5.18 eV for the boroxine- and borazine-cages, respectively. Our findings provide insights into the design and properties of highly porous boroxine and borazine cages for nanoscience.

A series of bis- N -substituted tetrandrine derivatives carrying different aromatic substituents attached to both nitrogen atoms of the natural alkaloid were studied with double-stranded model DNAs (dsDNAs) to examine the binding properties and mechanism. Variable-temperature molecular recognition studies using UV-vis and fluorescence techniques revealed the thermodynamic parameters, Δ H , Δ S , and Δ G , showing that the tetrandrine derivatives exhibit high affinity toward dsDNA ( K ≈ 10 5 -10 7 M -1 ), particularly the bis(methyl)anthraquinone (BAqT) and bis(ethyl)indole compounds (BInT). Viscometry experiments, ethidium displacement assays, and molecular modeling studies enabled elucidation of the possible binding mode, indicating that the compounds exhibit a synergic interaction mode involving intercalation of one of the N -aryl substituents and interaction of the molecular skeleton in the major groove of the dsDNA. Cytotoxicity tests of the derivatives with tumor and nontumor cell lines demonstrated low cytotoxicity of these compounds, with the exception of the bis(methyl)pyrene (BPyrT) derivative, which is significantly more cytotoxic than the remaining derivatives, with IC 50 values against the LS-180, A-549, and ARPE-19 cell lines that are similar to natural tetrandrine. Finally, complementary electrochemical characterization studies unveiled good electrochemical stability of the compounds., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Cocrystallizations of diboronic acids [1,3-benzenediboronic acid (1,3-bdba), 1,4-benzenediboronic acid (1,4-bdba) and 4,4'-biphenyldiboronic acid (4,4'-bphdba)] and bipyridines [1,2-bis(4-pyridyl)ethylene (bpe) and 1,2-bis(4-pyridyl)ethane (bpeta)] generated the hydrogen-bonded 1 : 2 cocrystals [(1,4-bdba)(bpe) 2 ] (1), [(1,4-bdba)(bpeta) 2 ] (2), [(1,3-bdba)(bpe) 2 (H 2 O) 2 ] (3) and [(1,3-bdba)(bpeta) 2 (H 2 O)] (4), wherein 1,3-bdba involved hydrated assemblies. The linear extended 4,4'-bphdba exhibited the formation of 1 : 1 cocrystals [(4,4'-bphdba)(bpe)] (5) and [(4,4'-bphdba-me)(bpeta)] (6). For 6, a hemiester was generated by an in-situ linker transformation. Single-crystal X-ray diffraction revealed all structures to be sustained by B(O)-H⋅⋅⋅N, B(O)-H⋅⋅⋅O, O w -H⋅⋅⋅O, O w -H⋅⋅⋅N, C-H⋅⋅⋅O, C-H⋅⋅⋅N, π⋅⋅⋅π, and C-H⋅⋅⋅π interactions. The cocrystals comprise 1D, 2D, and 3D hydrogen-bonded frameworks with components that display reactivities upon cocrystal formation and within the solids. In 1 and 3, the C=C bonds of the bpe molecules undergo a [2+2] photodimerization. UV radiation of each compound resulted in quantitative conversion of bpe into cyclobutane tpcb. The reactivity involving 1 occurred via 1D-to-2D single-crystal-to-single-crystal (SCSC) transformation. Our work supports the feasibility of the diboronic acids as formidable structural and reactivity building blocks for cocrystal construction., (© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Nanoconfinement is a recent strategy to enhance solubility and dissolution of active pharmaceutical ingredients (APIs) with poor biopharmaceutical properties. In this work, we combine the advantage of cocrystals of racemic praziquantel (PZQ) containing a water-soluble coformer (i.e., increased solubility and supersaturation) and its confinement in a mesoporous silica material (i.e., increased dissolution rate). Among various potential cocrystalline phases of PZQ with dicarboxylic acid coformers, the cocrystal with glutaric acid (PZQ-GLU) was selected and successfully loaded by the melting method into nanopores of SBA-15 (experimental pore size of 5.6 nm) as suggested by physical and spectroscopic characterization using various complementary techniques like N 2 adsorption, powder X-ray diffraction (PXRD), infrared spectroscopy (IR), solid-state NMR (ss-NMR), differential scanning calorimetry (DSC), and field emission-scanning electron microscopy (FE-SEM) analysis. The PZQ-GLU phase confined in SBA-15 presents more mobility according to ss-NMR studies but still retains its cocrystal-like features in the IR spectra, and it also shows depression of the melting transition temperature in DSC. On the contrary, pristine PZQ loaded into SBA-15 was found only in the amorphous state, according to the aforementioned studies. This dissimilar behavior of the composites was attributed to the larger crystal lattice of PZQ over the PZQ-GLU cocrystal (3320.1 vs 1167.9 Å 3 ) and to stronger intermolecular interactions between PZQ and GLU, facilitating the confinement of a more mobile solid-like phase in the constrained channels. Powder dissolution studies under extremely nonsink conditions (SI = 0.014) of the confined PZQ-GLU and amorphous PZQ phases embedded in mesoporous silica showed transient supersaturation behavior when dissolving in simulated gastric fluid (HCl pH 1.2 at 37 ± 0.5 °C) in a similar fashion to the bare cocrystal PZQ-GLU. A comparison of the area under the curve (AUC 0-90 min ) of the dissolution profiles afforded a dissolution advantage of 2-fold ( p < 0.05) of the new solid phases over pristine racemic PZQ after 90 min; under these conditions, the solubilized API reprecipitated as the recently discovered PZQ hemihydrate (PZQ-HH). In the presence of a cellulosic polymer, sustained solubilization of PZQ from composites SBA-15/PZQ or SBA-15/PZQ-GLU was observed, increasing AUC 0-90 min up to 5.1-fold in comparison to pristine PZQ. The combination of a confined solid phase in mesoporous silica and a methylcellulose polymer in the dissolution medium effectively maintained the drug solubilized during times significant to promote absorption. Finally, powder dissolution studies under intermediate nonsink conditions (SI = 1.99) showed a fast release profile from the nanoconfined PZQ-GLU phase in SBA-15, which reached rapid saturation (95% drug dissolved at 30 min); the amorphous PZQ composite and bare PZQ-GLU also displayed an immediate release of the API but at a lower rate (69% drug dissolved at 30 min). In all of these cases, a large dissolution advantage was observed from any of the novel solid phases over PZQ.

A cocrystal of the antihypertensive drug chlorthalidone (CTD) with caffeine (CAF) was obtained (CTD-CAF) by the slurry method, for which a 2:1 stoichiometric ratio was found by powder and single-crystal X-ray diffraction analysis. Cocrystal CTD-CAF showed a supramolecular organization in which CAF molecules are embedded in channels of a 3D network of CTD molecules. The advantage of the cocrystal in comparison to CTD is reflected in a threefold solubility increase and in the dose/solubility ratios, which diminished from near-unit values for D 0D to 0.29 for D 0CC . Furthermore, dissolution experiments under non-sink conditions showed improved performance of CTD-CAF compared with pure CTD. Subsequent studies showed that CTD-CAF cocrystals transform to CTD form I where CTD precipitation inhibition could be achieved in the presence of pre-dissolved polymer HPMC 80-120 cPs, maintaining supersaturation drug concentrations for at least 180 min. Finally, dissolution experiments under sink conditions unveiled that the CTD-CAF cocrystal induced, in pH-independent manner, faster and more complete CTD dissolution when compared to commercial tablets of CTD. Due to the stability and dissolution behavior of the novel CTD-CAF cocrystal, it could be used to develop solid dosage forms using a lower CTD dose to obtain the same therapeutic response and fewer adverse effects.

Hydrolysis reactions of di- and trinuclear organotin halides yielded large novel cage compounds containing Sn-O-Sn bridges. The molecular structures of two octanuclear tetraorganodistannoxanes showing double-ladder motifs, viz., [{Me 3 SiCH 2 (Cl)SnCH 2 YCH 2 Sn(OH)CH 2 SiMe 3 } 2 (μ-O) 2 ] 2 [1, Y=p-(Me) 2 SiC 6 H 4 -C 6 H 4 Si(Me) 2 ] and [{Me 3 SiCH 2 (I)SnCH 2 YCH 2 Sn(OH)CH 2 SiMe 3 } 2 (μ-O) 2 ] 2 ⋅0.48 I 2 [2⋅0.48 I 2 , Y=p-(Me) 2 SiC 6 H 4 -C 6 H 4 Si(Me) 2 ], and the hexanuclear cage-compound 1,3,6-C 6 H 3 (p-C 6 H 4 Si(Me) 2 CH 2 Sn(R) 2 OSn(R) 2 CH 2 Si(Me) 2 C 6 H 4 -p) 3 C 6 H 3 -1,3,6 (3, R=CH 2 SiMe 3 ) are reported. Of these, the co-crystal 2⋅0.48 I 2 exhibits the largest spacing of 16.7 Å reported to date for distannoxane-based double ladders. DFT calculations for the hexanuclear cage and a related octanuclear congener accompany the experimental work., (© 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

The dianionic aza crown ether-dtc N , N '-bis(dithiocarbamate)-1,10-diaza-18-crown-6 ( L 2- ) is a versatile ligand capable of yielding binuclear complexes with group 10 elements, also known as Ni-triade, [μ-(κ 2 -S,-S '- L )M 2 (PPh 3 ) 4 ]Cl 2 (M = Pd ( 1 ), Pt ( 2 )), [μ-(κ 2 -S,-S '-L)M 2 (PPh 3 ) 4 ](BPh 4 ) 2 (M = Pd ( 3 ), Pt ( 4 )), and μ-( κ-S,-S '-L)Ni 2 (PPh 3 ) 2 Cl 2 ( 5 ), and has proven to be an excellent option to the design of metal-based drugs able to provide multiple response to cell resistance. Palladium and platinum complexes, 1 and 2 , were tested for cytotoxicity in the human cervix carcinoma cell line HeLa-229, the human ovarian carcinoma cell line A2780, and the cisplatin-resistant mutant A2780 cis , finding significant activity toward all three cancer cell lines, with low micromolar IC 50 values, comparable to cisplatin. Markedly, against the cisplatin resistant cell line A2780 cis , compound 2 exhibits better cytotoxic activity than the clinical drug (IC 50 = 2.3 ± 0.2 μM for 2 versus 3.6 ± 0.5 μM for cisplatin). Moreover, an enhancement of the antitumor response is achieved when adding an equimolar amount of alkali metal chloride (NaCl or KCl) to the medium, for instance, testing compound 1 against the cisplatin-resistant A2780 cis cells, the IC 50 decreases from 9.3 ± 0.4 to 7.4 ± 0.3 and 5.4 ± 0.1 μM, respectively, after addition of the salt solution. For the platinum derivative 2 , the IC 50 improves by ca. 40% reaching 1.3 ± 0.1 μM when potassium chloride is added. Likewise, the resistant factor found for 2 (RF = 1) confirms that this complex circumvents cisplatin-resistance in A2780 cis and is improved with the addition of potassium chloride (RF = 0.65). The presence of the aza crown ether moiety as linker in the systems studied herein is a key point since, in addition to allowing and facilitating interaction with alkali metal ions, this unit is flexible enough to adapt to a variety of environments, as confirmed by the X-ray crystal structures described, where different conformations and ways to fold in are found. In order to gain insight into the electronic and structural facts involved in the interaction of complex 2 with the alkali metal ions, a DFT study was performed, and the description of the molecular electrostatic potentials (MEPs) is also presented.

The thermodynamic stability of 1 : 1 and 2 : 1 boron-nitrogen (B←N) adducts formed between aromatic boronic esters with mono- and diamines was studied in solution by NMR and UV-vis spectroscopy with association energies (ΔG°) ranging from -11 to -28 kJ mol -1 . The effect of different substituents in the boronic ester, the nature of the diamine linker, and the effect of the solvent was explored. Stable 2 : 1 B←N adducts with diamines such as 1,3-diaminopropane were produced in solutions of hydrogen-bonding acceptor solvents (acetonitrile and ethyl acetate), which can be isolated in the solid state as crystalline solvates, whereas the use of noncoordinating solvents such as 1,2-dichloroethane afforded mainly 1 : 1 B←N adducts. In suitable combinations, aromatic bis-pyridyl diamines produced stable 2 : 1 B←N adducts that were isolated either as solvent-free solids, solvates, or cocrystals. In these crystalline forms, double-tweezer hosts were observed with an exceptional syn/anti conformational guest-adaptability driven by simultaneous donor-acceptor and C-H⋅⋅⋅π interactions in the tweezer cavities, resembling preorganized covalent tweezer hosts. Interestingly, cocrystals with electron-rich guests such as tetrathiafulvalene and pyrene showed non-centrosymmetric crystal lattices with infinite π-stacked donor-acceptor columns., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The effect of hydroxypropyl methylcellulose (HPMC) and methylcellulose (Methocel ® 60 HG) on the dissolution behavior of two cocrystals derived from nitazoxanide (NTZ), viz., nitazoxanide-glutaric acid (NTZ-GLU, 1:1) and nitazoxanide-succinic acid (NTZ-SUC, 2:1), was explored. Powder dissolution experiments under non-sink conditions showed similar dissolution profiles for the cocrystals and pure NTZ. However, pre-dissolved cellulosic polymer in the phosphate dissolution medium (pH 7.5) modified the dissolution profile of NTZ when starting from the cocrystals, achieving transient drug supersaturation. Subsequent dissolution studies under sink conditions of polymer-based pharmaceutical powder formulations with NTZ-SUC cocrystals gave a significant improvement of the apparent solubility of NTZ when compared with analogous formulations of pure NTZ and the physical mixture of NTZ and SUC. Scanning electron microscopy and powder X-ray diffraction analysis of samples recovered after the powder dissolution studies showed that the cocrystals undergo fast dissolution, drug supersaturation and precipitation both in the absence and presence of polymer, suggesting that the solubilization enhancement is due to polymer-induced delay of nucleation and crystal growth of the less soluble NTZ form. The study demonstrates that the incorporation of an appropriate excipient in adequate concentration can be a key factor for inducing and maintaining the solubilization of poorly soluble drugs starting from co-crystallized solid forms. In such a way, cocrystals can be suitable for the development of solid dosage forms with improved bioavailability and efficacy in the treatment of important parasitic and viral diseases, among others.

With the objective of studying the conformational and macrocyclic effects of selected metal chelates on their peroxidase activities, Cu 2+ and Fe 3+ complexes were synthesized with a macrocyclic derivative of ethylenediaminetetraacetic acid and o -phenylenediamine (abbreviated as edtaodH 2 ) and its new open-chain analogue (edtabzH 2 ). The Fe 3+ complex of edtaodH 2 has a peroxidase-like activity, whereas the complex of edtabzH 2 does not. The X-ray study of the former shows the formation of a dimeric molecule {[Fe(edtaod)] 2 O} in which each metal with an octahedral coordination is overposed over the macrocyclic cavity, as a result of rigid macrocyclic frame, to form an Fe-O-Fe bridge; the exposure of the central metal to the environment facilitates the capture of oxygen to drive the biomimetic activity. The peroxidase-inactive Fe 3+ complex consists of a mononuclear complex ion [Fe(edtabz)(H 2 O)] + , the metal ion of which is suited in a distorted pentagonal bipyramid to be protected from environmental oxygen. The copper(II) complexes, which have mononuclear structures with high thermodynamic stability compared with the iron(III) complexes, show no peroxidase activity. The steric effects play a fundamental role in the biomimetic activity., Competing Interests: The authors declare no competing financial interest., (Copyright © 2019 American Chemical Society.)

We report channel confinement properties of an electron-deficient boron host derived from the orthogonal B←N interaction between a boronic ester and trans -pentafluorostilbazole. The boron host forms one-dimensional channels in the crystalline solid state when crystallized with common electron-rich aromatic petrochemicals (i.e., benzene, toluene, o -xylene) to form solvates and a cocrystal with stilbene. Molecular confinement of the electron-rich molecules in the solids is achieved through a combination of aryl-perfluoroaryl interactions (π-π F ) and hydrogen bonds., (Copyright © 2019 Campillo-Alvarado, D'mello, Sinnwell, Höpfl, Morales-Rojas and MacGillivray.)

Crystalline framework materials have gained interest because of their many potential applications. A novel chiral tetrandrine salt (DNT) has been synthesized and characterized by conventional analytical techniques and single-crystal X-ray diffraction analysis, and its self-assembly behavior studied. In the solid state, 48 molecules of the compound self-assemble into an organic framework based on nanospherical aggregates formed exclusively through weak noncovalent interactions. Additionally, it was demonstrated by UV-vis spectroscopy and TGA that assembled DNT can include the Nile Red dye, giving a fluorescent material. To the best of our knowledge, these spherical assemblies are the largest among the purely synthetic organic self-assembled molecular crystals reported to date., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

B←N coordination supports a [2+2] photodimerization in the solid state. The bond is defined by an orthogonal interaction between stilbazole and a phenylboronic ester to enable a stereocontrolled and rapid photoreaction. The cyclobutane photoproduct affords a novel diboron bis-tweezer adduct that is used to separate a mixture of benzene and thiophene upon crystallization., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

In this work, we report on the synthesis of two new mono-alkylated tetrandrine derivatives with acridine and anthracene units, MAcT and MAnT. The compounds were fully characterized by physicochemical techniques and single-crystal X-ray diffraction analysis. In addition, both derivatives were studied as nucleotide receptors and double-stranded DNA binders in aqueous phosphate buffer at pH = 7.2 using UV-vis and fluorescence spectroscopy. According to the molecular recognition studies, MAcT and MAnT exhibit high affinity (K ∼ 10 5  M -1 ) and selectivity for ds-DNA, presumably in an intercalation mode. Finally, the anti-proliferative effects of the tetrandrine derivatives on different cancer cell lines were explored, revealing promising activities. Particularly, the mono-anthracene tetrandrine derivative MAnT showed an IC 50 of 2.74 μg/mL on the HeLa cervical cancer cell line, representing a value 3.3 times smaller than that obtained for unsubstituted tetrandrine. Examination of the cytotoxic effects on the HeLa cell line by inverted microscopy suggests that the cell death mechanism consists basically in apoptosis. The molecular modelling of three ds-DNA-MAcT complexes, suggested that the macrocycles may use an intercalation binding mode towards DNA. MAcT is predicted to bind into the major groove of the ds-DNA providing non-covalent interactions such as electrostatic, van der Waals and hydrophobic interactions that lead to selectivity. Overall experimental data supports the mode of action of MAnT and MAcT as cytotoxic compounds against cancer cell lines via a DNA interaction mechanism., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Boronic esters are useful building blocks for crystal engineering and the generation of supramolecular architectures, including macrocycles, cages and polymers (one-, two- and three-dimensional), with potential utility in diverse fields such as separation, storage and luminescent materials. The novel dinuclear cyanophenylboronic ester described herein, namely 4,4'-(2,4,8,10-tetraoxa-3,9-diboraspiro[5.5]undecane-3,9-diyl)dibenzonitrile, C 19 H 16 B 2 N 2 O 4 , was prepared by condensation of 4-cyanophenylboronic acid and pentaerythritol and fully characterized by elemental analysis, IR and NMR ( 1 H and 11 B) spectroscopy, single-crystal X-ray diffraction analysis and TG-DSC (thermogravimetry-differential scanning calorimetry) studies. In addition, the photophysical properties were examined in solution and in the solid state by UV-Vis and fluorescence spectroscopies. Density functional theory (DFT) calculations with ethanol as solvent reproduced reasonably well the HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) of the title compound. Hirshfeld surface and fingerprint plot analyses are presented to illustrate the supramolecular connectivity in the solid state.

Di- and trinuclear organotin(IV) complexes, in which the metal atoms are separated by large aromatic connectors, are useful building blocks for self-assembly. This is demonstrated by the preparation of [1+1], [2+2], and [2+3] macrocyclic and cage-type structures in combination with organic aromatic dicarboxylates. The linkage of the metal atoms by organic binders and the option of varying the number of reactive M-X sites generate versatile building blocks enabling molecular tectonics instead of the node-based strategy generally employed in metallo-supramolecular self-assembly., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)