https://pubs.rsc.org/en/content/articlepdf/2019/NP/C8NP00092A

Marine natural products.

This critical review presents a comprehensive study of transition-metal carboxylate clusters which may serve as secondary building units (SBUs) towards construction and synthesis of metal–organic frameworks (MOFs). We describe the geometries of 131 SBUs, their connectivity and composition. This contribution presents a comprehensive list of the wide variety of transition-metal carboxylate clusters which may serve as secondary building units (SBUs) in the construction and synthesis of metal–organic frameworks. The SBUs discussed here were obtained from a search of molecules and extended structures archived in the Cambridge Structure Database (CSD, version 5.28, January 2007) which included only crystals containing metal carboxylate linkages (241 references).

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Secondary building units, nets and bonding in the chemistry of metal–organic frameworks

In 1981, the macrocyclic methylene-bridged glycoluril hexamer (CB[6]) was dubbed "cucurbituril" by Mock and co-workers because of its resemblance to the most prominent member of the cucurbitaceae family of plants--the pumpkin. In the intervening years, the fundamental binding properties of CB[6]-high affinity, highly selective, and constrictive binding interactions--have been delineated by the pioneering work of the research groups of Mock, Kim, and Buschmann, and has led to their applications in waste-water remediation, as artificial enzymes, and as molecular switches. More recently, the cucurbit[n]uril family has grown to include homologues (CB[5]-CB[10]), derivatives, congeners, and analogues whose sizes span and exceed the range available with the alpha-, beta-, and gamma-cyclodextrins. Their shapes, solubility, and chemical functionality may now be tailored by synthetic chemistry to play a central role in molecular recognition, self-assembly, and nanotechnology. This Review focuses on the synthesis, recognition properties, and applications of these unique macrocycles.

The cucurbit[n]uril family

Computational Prediction of 1H and 13C Chemical Shifts: A Useful Tool for Natural Product, Mechanistic, and Synthetic Organic Chemistry

This review highlights the past six year advances in the blossoming field of cucurbit[n]uril chemistry. Because of their exceptional recognition properties in aqueous medium, these pumpkin-shaped macrocycles have been generating some tremendous interest in the supramolecular community. They have also become key units in various self-organizing and stimulus-controlled assemblies, as well as in advanced materials and drug carriers. The scope of this review is limited to the main family of cucurbit[n]urils (n = 5, 6, 7, 8, 10). The reader will find an overview of their preparation, their physicochemical and biological properties, as well as their recognition abilities towards various organic and inorganic guests. Detailed thermodynamic and kinetic considerations, as well as multiple applications including supramolecular catalysis are also discussed.

Cucurbituril chemistry: a tale of supramolecular success

The chemisorption binding of gold(III) by freshly precipitated binuclear zinc dithiocarbamates [Zn2(S2CNR2)4] from solutions in 2 M HCl makes it possible to obtain heteroligand complexes [Au(S2CNR2)Cl2]: R = CH3 (I), iso-C3H7 (II); R2 = (CH2)6 (III). The structural organization of complexes I, II, and III is determined by X-ray diffraction analysis (CIF files CCDC no. 1813107, 1813369, and 1813108, respectively). The distorted square–planar structure of the cis-[AuS2Cl2] chromophores shows the low-spin dsp2-hybrid state of the central gold atom. Pairwise secondary interactions Au⋅⋅⋅S between the adjacent molecules in complexes I and III result in the building of zigzag polymer chains (⋅⋅⋅[Au{S2CN(CH3)2}Cl2]⋅⋅⋅)n and binuclear aggregates [Au{S2CN(CH2)6}Cl2]2 at the supramolecular level. Complex II is presented by discrete molecules [Au{S2CN(iso-C3H7)2}Cl2]. According to the simultaneous thermal analysis data, the single final product of the thermolysis of compounds I–III is reduced elemental gold.

Heteroleptic Dithiocarbamato–Chlorido Gold(III) Complexes [Au(S 2 CNR 2 )Cl 2 ] (R = CH 3 , iso -C 3 H 7 ; R 2 = (CH 2 ) 6 ): Synthesis, Supramolecular Structures, and Thermal Behavior

Synthesis, X-ray diffraction, IR and luminescence spectroscopic studies of the monohydrate of pentachloroantimonate(III) of doubly protonated ciprofloxacin (C17H19N3O3F)SbCl5 · H2O (I) were performed. The structure of I is formed by SbCl6 octahedra combined into polymeric chains [SbCl5]n2n− through common vertices, ciprofloxacinium cations (CfH3)2+, and water molecules linked by hydrogen bonds. CfH is protonated at the carbonyl oxygen atom and the terminal nitrogen atom of the piperazinyl group. The electronic and geometric aspects determining the luminescence properties of I and of related compounds are discussed.

Crystal structure and spectroscopic properties of ciprofloxacinium pentachloroantimonate(III) monohydrate (C17H19N3O3F)SbCl5 · H2O

Fluoridezirconate crystallohydrates ZnZrF6 · nH2O (n = 6–2) and anhydrous ZnZrF6 are investigated by vibrational spectroscopy and thermography. The influence of the hydrate number on the structure of the cationic and anionic sublattices of the crystallohydrates is studied. The changes in the strength of HOH···F and HOH···O hydrogen bonds of coordinated and outer-sphere water molecules occurring with variations in the hydrate number are determined by changes in the IR spectra. The IR spectra of ZnZrF6 · nH2O (n =6, 4) compounds, which have isolated complex anions [ZrF6]2– in their structure, revealed a band with two peaks in the range of 3470–3430 cm–1, which corresponds to stretching vibrations of coordinated water molecules. The spectra of ZnZrF6 · nH2O (n = 5, 3, 2, 1) crystallohydrates with a polymeric structure show a high-frequency shift of this band, which corresponds to weakening of hydrogen bonds. The vibrations of crystallization water molecules involved in the network of strong O–H···F and O–H···O hydrogen bonds manifest themselves in the spectra of ZnZrF6 · nH2O (n =5, 3) crystallohydrates by broad structureless bands in the region of stretching, bending, and libration vibrations.

Structure of ZnZrF 6 · n H 2 O ( n = 6–2) and ZnZrF 6 crystallohydrates according to vibrational spectroscopy data

Crystals of MnNbOF5 · 4H2O were studied by X-ray diffraction, differential scanning calorimetry (DSC) and thermogravimetry. DSC showed a phase transition in the temperature range of 282 to 296.3 K. The compound is dehydrated in two stages in the temperature ranges of 65–131.1 and 131.1–190°C, two H2O molecules being removed in each stage. The structure of MnNbOF5 · 4H2O was determined at 153 K (α phase; space group P21/c) and at 297 K (β phase, space group C2/m). The structure of both phases is formed of the octahedral complexes [NbF4(O/F)2/2]0.5− and [Mn(H2O)4(O/F)2/2]0.5+ linked by bridging O and F atoms to infinite chains. The isolated niobium-manganese chains are connected by O-H…F hydrogen bonds. In the α phase, the Nb, O, and F atoms in the trans position relative to O are disordered with respect to the inversion center of the structure. Transition to the β phase is accompanied by splitting of all ligand positions at the Nb and Mn atoms into two equally probable positions.

Andrey V. Gerasimenko

Papers

Heteroleptic Dithiocarbamato–Chlorido Gold(III) Complexes [Au(S 2 CNR 2 )Cl 2 ] (R = CH 3 , iso -C 3 H 7 ; R 2 = (CH 2 ) 6 ): Synthesis, Supramolecular Structures, and Thermal Behavior

Crystal structure and spectroscopic properties of ciprofloxacinium pentachloroantimonate(III) monohydrate (C17H19N3O3F)SbCl5 · H2O

Structure of ZnZrF 6 · n H 2 O ( n = 6–2) and ZnZrF 6 crystallohydrates according to vibrational spectroscopy data

Crystal structures of MnNbOF5 · 4H2O at 153 and 297 K

Synthesis and investigation of a new coordination compound: Ammonium octafluoridoindate-zirconate heptahydrate NH4InZrF8·7H2O