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The reaction of the bicyclic silicon(I) ring compound Si4{N(SiMe3)Mes}41 with strong zwitterionic character and moderate sterical demand of the amido substituents with two equivalents of KC8 was investigated. This resulted in the unexpected abstraction of two amido substituents from 1 and additionally in dimerization to a dianionic Si8 cluster compound 2 with four unsubstituted silicon atoms and two [K([18]crown‐6)]+ counter cations. Performing this reaction in the absence of [18]crown‐6 results in release of only one amido substituent from 1 and dimerization to a dianionic Si8 cluster 3 with only two unsubstituted silicon atoms. This reaction with KC8 was repeated and trapping agents such as SiMe3Cl and tBuCl were added in‐situ whereupon the second isolated homocyclic silylene 4 and a monoanionic hydride and tBu substituted Si8 cluster 5 with one unsubstituted silicon atom were isolated. Furthermore, 1 was reacted with KOtBu which resulted in the selective abstraction of one SiMe3 group and formation of the tetrahedral silanide 6 with one imido substituent bridging an edge of the tetrahedron. [ABSTRACT FROM AUTHOR]

Two tetranuclear Co(II) complexes, [Co4(pmab)4Cl4] (1) and [Co4(pmab)4(OBz)2]Cl2 (2) [Hpmab = 2-{(p-pyridinylmethylene)amino}benzenemethanol], have been synthesized and characterized through single-crystal X-ray diffraction, IR and UV-VIS spectroscopy, and magnetic measurements. Structural analysis revealed that both complexes possess a [Co4O4] cubane-like metal core connected by μ3-alkoxo bridges. Magnetic measurements of Complex 1 indicate weak ferromagnetic interactions (J ~ +0.75 cm−1) within the tetranuclear core, while Complex 2 exhibits antiferromagnetic behavior due to the presence of syn-syn bridging benzoate ligands. Alternating current (AC) magnetic measurements suggest that Complex 1 exhibits slow magnetic relaxation behavior. [ABSTRACT FROM AUTHOR]

To harness the full potential of electrochemical water splitting for hydrogen and oxygen production, recent efforts have focused on the development of single atom catalysts (SACs) to enhance electrocatalytic performance while maximizing metal atom utilization. In this context, we have designed and assessed the feasibility of late first-row transition metal (TM) linked 1-Azahomocubane dimer as SACs for facilitating the water splitting reaction. The effectiveness of these designed electrocatalysts has been thoroughly evaluated through density functional theory (DFT) calculations. Remarkably, the Fe containing SAC demonstrated exceptional activity towards the hydrogen evolution reaction (HER) (ΔG H = −0.06), indicating the ability of Fe metal to facilitate the adsorption of hydrogen ions and their release as hydrogen gas. Furthermore, the Fe containing SAC revealed high stability and sufficient conductivity. This investigation underscores the potential utility of the Fe containing SAC as effective precious-metal free electrocatalysts for the HER. [Display omitted] • TM linked 1-Azahomocubane dimer SAC for water the splitting reactions. • Fe@2Cubane revealed ultra-high catalytic activity toward the HER. • The Fe based SACs serves as precious-metal free, chemically stable, and sufficiently conductive SACs. [ABSTRACT FROM AUTHOR]

[M4O4] (M = 3d transition metal) represents an interesting class of compounds featuring cubane-type molecular structures, and particularly, [Mn4O4] cubanes or their derivatives attract much attention by virtue of their potential applications as single-molecule magnets (SMMs) or catalysts. However, the rational design of desired cubane-related structures is still a challenging subject due to the lack of readily available methods to effectively tune the construction patterns of the molecule assembly. In this work, we report the employment of different alcohols to prepare three cubane-related molecules, Mn2(dhd)4(iPrOH)2 (1), Mn4(dhd)4(OEt)4(EtOH)4 (2) and Mn4(dhd)6(OMe)2(MeOH)2 (3) (dhd = 5,5-dimethyl-2,4-hexanedione). Interestingly, the bulkiest iPrOH leads to simple rhombic dimer molecule 1. It can be deemed a rudimentary structure oftetranuclear [Mn4O4] cubane 2, which can be realized by the use of less bulky EtOH. In addition, the least bulky MeOH promotes the assembly of the cubanes, eventually bringing about defective dicubane molecular cluster 3. The accurate crystal structures of 1–3 were modeled by single-crystal X-ray diffraction, and their electronic structures were investigated through absorption spectroscopy coupled with theoretical calculations. Overall, this work demonstrates a systematic study on controlling cubane-type structures of Mn-based compounds by applying different solvents, which provides a new means to design functional molecules for specific applications. [ABSTRACT FROM AUTHOR]

Two tetranuclear Co(II) complexes, [Co4(pmab)4Cl4] (1) and [Co4(pmab)4(OBz)2]Cl2 (2) [Hpmab = 2-{(p-pyridinylmethylene)amino}benzenemethanol], have been synthesized and characterized through single-crystal X-ray diffraction, IR and UV-VIS spectroscopy, and magnetic measurements. Structural analysis revealed that both complexes possess a [Co4O4] cubane-like metal core connected by μ3-alkoxo bridges. Magnetic measurements of Complex 1 indicate weak ferromagnetic interactions (J ~ +0.75 cm−1) within the tetranuclear core, while Complex 2 exhibits antiferromagnetic behavior due to the presence of syn-syn bridging benzoate ligands. Alternating current (AC) magnetic measurements suggest that Complex 1 exhibits slow magnetic relaxation behavior.

The selective synthesis of cage‐type hydrocarbons through the editing of the highly symmetric molecule cubane can be anticipated as one of the efficient approaches. In this paper, we identify a catalyst that facilitates the efficient scaffold isomerization of cubanes into homocubanes. This approach, which involves the direct synthesis of homocubanol esters, is promising as a novel method for the synthesis of phenoxy bioisosteres. Additionally, we observed that the isomerization of 1,4‐bis(acyloxymethl)cubane results in the generation of both D2‐ and C2‐symmetrical bishomocubanes. The same catalyst was also applied to the isomerization of acyloxymethylcuneanes, producing homocuneanol esters. [ABSTRACT FROM AUTHOR]

Small polyhedral hydrocarbons represented by cubane have attracted attention as potential molecular scaffolds for pharmaceuticals as benzene bioisoster. Cubane is also expected to be used as a chiral scaffold, but due to its high symmetry, it is necessary to introduce chirality by sequential site‐selective introduction of substituents. Furthermore, polyhedral desymmetrized isomers of cubane, such as cuneane and semibullvalene, and extended cage compounds, such as bishomocubane and homocuneane, exhibit chirality and are also expected to be used as new optically active scaffolds. In this concept, we would like to explain the synthetic routes we have planned, specifically, the decoration and editing of the cubane skeleton. [ABSTRACT FROM AUTHOR]

Functionalized cubanes are attractive scaffolds for medicinal chemists as they are bioisosteres of benzene rings. The replacement of a benzene ring by a cubane, in a bioactive compound, can have a beneficial effect on the biological activity of such compound. Thus, the design of new molecular cubyl building blocks is of importance. In this review, we will focus on the functionalization of cubanes by creating C−C, C−heteroatom bonds e. g. C−N, C−O, C−B, C−P and C−S bonds. Different methods are reported involving organometallics, radicals, and ionic species. Mechanisms are included when relevant. [ABSTRACT FROM AUTHOR]

Synthesis, structure, and magnetic properties of a tetranuclear metal complex with a symmetrical polydentate ligand, trans-(±)-1,2-(2-hydroxy-3-methoxybenzamido)cyclohexane (H2L), were characterized. The complexes have tetranuclear cubane cores with the formulae [Ni4(L)2(μ3-OMe)4(CH3OH)4] (1) and [Cu4(L)2(μ3-OMe)4(CH3OH)2] (2), whose cluster units are each composed of chiral ligands [(R, R)- or (S, S)-L]. The magnetic properties of the two compounds were characterized by 1 being ferromagnetic and 2 being antiferromagnetic. [ABSTRACT FROM AUTHOR]

Homocubane, a highly strained cage hydrocarbon, contains two very different positions for the introduction of a nitrogen atom into the skeleton, e. g. a position 1 exchange results in a tertiary amine whereas position 9 yields a secondary amine. Herein reported is the synthesis of 9‐azahomocubane along with associated structural characterization, physical property analysis and chemical reactivity. Not only is 9‐azahomocubane readily synthesized, and found to be stable as predicted, the basicity of the secondary amine was observed to be significantly lower than the structurally related azabicyclo[2.2.1]heptane, although similar to 1‐azahomocubane. [ABSTRACT FROM AUTHOR]

This document provides a comprehensive overview of the synthesis and chemistry of cubane, a molecule with a unique cubic structure. It discusses the challenges and methods involved in introducing substituents at different positions of cubane, as well as the synthesis of trisubstituted and tetrasubstituted cubanes. The document also acknowledges the contributions of Professor Eaton to cubane chemistry and expresses gratitude for his guidance and inspiration. This information is valuable for researchers interested in the functionalization of cubane. [Extracted from the article]

[M4O4] (M = 3d transition metal) represents an interesting class of compounds featuring cubane-type molecular structures, and particularly, [Mn4O4] cubanes or their derivatives attract much attention by virtue of their potential applications as single-molecule magnets (SMMs) or catalysts. However, the rational design of desired cubane-related structures is still a challenging subject due to the lack of readily available methods to effectively tune the construction patterns of the molecule assembly. In this work, we report the employment of different alcohols to prepare three cubane-related molecules, Mn2(dhd)4(iPrOH)2 (1), Mn4(dhd)4(OEt)4(EtOH)4 (2) and Mn4(dhd)6(OMe)2(MeOH)2 (3) (dhd = 5,5-dimethyl-2,4-hexanedione). Interestingly, the bulkiest iPrOH leads to simple rhombic dimer molecule 1. It can be deemed a rudimentary structure oftetranuclear [Mn4O4] cubane 2, which can be realized by the use of less bulky EtOH. In addition, the least bulky MeOH promotes the assembly of the cubanes, eventually bringing about defective dicubane molecular cluster 3. The accurate crystal structures of 1–3 were modeled by single-crystal X-ray diffraction, and their electronic structures were investigated through absorption spectroscopy coupled with theoretical calculations. Overall, this work demonstrates a systematic study on controlling cubane-type structures of Mn-based compounds by applying different solvents, which provides a new means to design functional molecules for specific applications.

The construction of cage-type hydrocarbon scaffolds, potential bioisosteres for benzene, often involves multiple steps, making their selective syntheses challenging. However, by employing a scaffold editing technique that leverages the isomerization of the highly symmetrical cubane as a precursor, these can be synthesized more efficiently with fewer steps. In this study, we present a method for the selective synthesis of semibullvalene-1,3-dicarboxylic acid with a good yield, starting from dimethyl cubane-1,4-dicarboxylate, using a reaction in hot water. [ABSTRACT FROM AUTHOR]

Pirfenidone, an oral anti‐fibrotic and anti‐inflammatory medication used for the treatment of idiopathic pulmonary fibrosis (IPF), has been proposed to treat post‐COVID pneumonia pulmonary fibrosis (PF). However, pirfenidone displays side effects which include hepatotoxicity and anorexia. Cubane and cyclooctatetraene (COT) derivatives of pirfenidone were prepared as bioisostere/biomotif replacements of the phenyl ring to explore potential changes in activity. The key intermediate, aminocubane, enabled the synthesis of both the cubane and cyclooctatetraene (COT) derived pirfenidone analogues in 6 steps. The COT derivative was observed to display similar activity and cytotoxicity with pirfenidone in an anti‐virus and ACE2 inhibition assay, although limited effect was observed from pirfenidone and the analogues described herein. [ABSTRACT FROM AUTHOR]

Monitoring of water oxidation by the established Co cubane catalyst Co4O4(OAc)4(py)4 (abbrev. Co4O4, OAc = acetate, py = pyridine) by time-resolved rapid-scan ATR FT-IR spectroscopy revealed the O-O bond forming intermediate by its O-O stretch mode at 833 cm-1. The catalysis was either driven in alkaline solution by a visible light sensitizer or in hydroxide (OH-) containing acetonitrile solution using the one-electron oxidized cubane as the sole source of charge. The μ-peroxido structure of the intermediate was established by 18O isotopic labeling, and its catalytic relevancy and role in the O2 evolving cycle were revealed by the kinetic relationship with decreasing cubium ([Co4O4]+) and recovery of the Co4O4 complex.

Four ways are introduced for the comparative prediction on solid phase heat of formation ΔHof (s) of cubane through different level of theories (B3LYP/6‐31G(d,p), B3LYP/6‐311+G(2d,2p), B3PW91/6‐31G(d,p), MP2/6‐31G(d,p), and G2). It is based on the heats of sublimation ΔHsub derived from information obtained from the quantum‐mechanically calculated electrostatic potential of each isolated molecule. The ΔHsub are combined with the aforementioned gas phase heats of formation ΔHof (g) to produce condensed phase heats of formation ΔHof (s). Comparisons of the methods are given, along with the recommendations about the methods that could produce better agreement with experiment, wishing to offer some beneficial references. [ABSTRACT FROM AUTHOR]

A major challenge to the implementation of artificial photosynthesis (AP), in which fuels are produced from abundant materials (water and carbon dioxide) in an electrochemical cell through the action of sunlight, is the discovery of active, inexpensive, safe, and stable catalysts for the oxygen evolution reaction (OER). Multimetallic molecular catalysts, inspired by the natural photosynthetic enzyme, can provide important guidance for catalyst design, but the necessary mechanistic understanding has been elusive. In particular, fundamental transformations for reactive intermediates are difficult to observe, and well-defined molecular models of such species are highly prone to decomposition by intermolecular aggregation. Here, we present a general strategy for stabilization of the molecular cobalt-oxo cubane core (Co4O4) by immobilizing it as part of metal-organic frameworks, thus preventing intermolecular pathways of catalyst decomposition. These materials retain the OER activity and mechanism of the molecular Co4O4 analog yet demonstrate unprecedented long-term stability at pH 14. The organic linkers of the framework allow for chemical fine-tuning of activity and stability and, perhaps most importantly, provide "matrix isolation" that allows for observation and stabilization of intermediates in the water-splitting pathway.

Metal ion interactions with nuclei acids and their constituents represent a multi-faceted and growing research field. This contribution deals with molecular recognition between synthetic purine 17 nucleosides and first-row transition metal complexes, with O- and/or N-amino chelators which are able to 18 engage in intra-molecular N-H···(N or O) and O-H···(N or O) interligand interactions. Crystals of these complexes can also display inter-molecular aromatic π-stacking and/or other non-conventional interactions. In this manuscript, we used 2-(2-aminoethoxy)ethanol (2aee) as a potential N,O(e),O(ol)-chelator for nickel(II). However, unexpectedly, the reaction between NiCl2, acyclovir (acv), and 2aee in methanol afforded parallelepiped apple-green crystals of [Ni(acv-H)(MeO)(H2O)]4·8H2O, (1) a tetranuclear molecule with an equimolar Ni(II):µ3-methanolate(1-):µ2-N7,O6-acyclovirate(1-) (acv-H) ratio. The µ2-N7,O6-(acv-H) metal-binding pattern (MBP) is unprecedented in terms of both its anionic and bridging roles. The single-crystal X-ray diffraction structure as well as thermogravimetric analysis and the (FT-IR +Vis-UV) spectra of 1 are reported. Theoretical density functional theory (DFT) calculations are used to analyse the antiparallel π-stacking interactions that govern the formation of self-assembled dimers in the solid state. [ABSTRACT FROM AUTHOR]

Studies on the preparation, structures, and properties of heterometallic complexes are currently of great interest because of their emergent synergistic properties. Although both rare earth and aluminum oxo clusters have been developed, only a few heterometallic compounds combine the two clusters. In this study, using “ligand-controlled partial hydrolysis”, we synthesize three hat-shaped cationic Al9Ln7 (Ln = Ce, Pr, Nd) clusters comprising tetrameric cubane units. Their unique vertex-to-edge-sharing arrangements have not been reported in either rare earth or aluminum oxo clusters. Apart from single-crystal X-ray diffraction, these compounds were characterized by Fourier transform infrared spectroscopy, powder X-ray diffraction, thermogravimetric analysis, and energy dispersive spectroscopy. Al9Ln7 clusters could serve as efficient catalysts for aldol condensation reactions between acetone and p-nitrobenzaldehyde under mild conditions, with an excellent yield of 86% by AlOC-129Ce.

In an attempt to isolate boron-containing tri-niobium polychalcogenide species, we have carried out prolonged thermolysis reactions of [Cp*NbCl4] (Cp* = ɳ5-C5Me5) with four equivalents of Li[BH2E3] (E = Se or S). In the case of the heavier chalcogen (Se), the reaction led to the isolation of the tri-niobium cubane-like cluster [(NbCp*)3(μ3-Se)3(BH)(μ-Se)3] (1) and the homocubane-like cluster [(NbCp*)3(μ3-Se)3(μ-Se)3(BH)(μ-Se)] (2). Interestingly, the tri-niobium framework of 1 stabilizes a selenaborate {Se3BH}− ligand. A selenium atom is further introduced between boron and one of the selenium atoms of 1 to yield cluster 2. On the other hand, the reaction with the sulfur-containing borate adduct [LiBH2S3] afforded the trimetallic clusters [(NbCp*)3(μ-S)4{μ-S2(BH)}] (3) and [(NbCp*)3(μ-S)4{μ-S2(S)}] (4). Both clusters 3 and 4 have an Nb3S6 core, which further stabilizes {BH} and mono-sulfur units, respectively, through bi-chalcogen coordination. All of these species were characterized by 11B{1H}, 1H, and 13C{1H} NMR spectroscopy, mass spectrometry, infrared (IR) spectroscopy, and single-crystal X-ray crystallography. Moreover, theoretical investigations revealed that the triangular Nb3 framework is aromatic in nature and plays a vital role in the stabilization of the borate, borane, and chalcogen units. [ABSTRACT FROM AUTHOR]

2,6‐Disubstituted cuneane has potential as a p‐disubstituted benzene bioisostere and a novel chiral scaffold. It is a constitutional isomer of a 1,4‐disubstituted cubane obtained via a metal‐catalyzed skeletal rearrangement. Unlike the highly symmetrical 1,4‐disubstituted cubane, the isomerized 2,6‐disubstituted cuneane is a chiral molecule possessing C2 symmetry. Examining various chiral catalysts revealed that the Pd‐pincer catalyst provides a good asymmetric induction. [ABSTRACT FROM AUTHOR]

Novel 1,4‐disubstituted cubane derivatives have been designed and selected ones have been successfully synthesized and characterized by various analytical and spectroscopic techniques, including single‐crystal X‐ray analysis. A detailed computational study at B3LYP/6‐311++G(d,p) level of theory revealed that all newly designed 1,4‐disubstituted cubane derivatives possess higher densities, higher density‐specific impulse and superior ballistic properties when compared to conventional fuels, for example, RP‐1. These compounds also exhibit acceptable kinetic and thermodynamic stabilities which were evaluated in terms of their HOMO‐LUMO energy gap and bond dissociation energies, respectively, and are superior to TEX and many other compounds containing explosophoric groups. These results provide novel insights into the possible application of cubane‐based energetic materials. [ABSTRACT FROM AUTHOR]

Novel organic materials have played a tremendous role in developing high-performance nonlinear optical materials. Herein, the geometric, electronic and nonlinear optical properties of designed alkali (Li, Na, and K) and alkaline earth metals (Be, Mg, and Ca) doped cubane (C8H8) complexes have been explored by using density functional theory. Excess electrons generated by doping alkali/alkaline earth metals have significantly enhanced the NLO properties by reducing the crucial excitation energy of the cubane. The HOMO–LUMO energy gap of doped complexes is reduced up to 4.43 eV. It is revealed that the reduction in the HOMO–LUMO energy gap results from the development of the new highest occupied molecular orbital, which is confirmed by the density of state (DOS) analysis. The NBO analysis is carried out to confirm the charge transfer between metal atoms and the cubane ring. Further, the NCI and QTAIM analyses confirmed the nature of intramolecular interaction. The remarkable first hyperpolarizability (βo) of 3.01 × 104 au is observed for K@Cubane. Moreover, frequency dependent first hyperpolarizability (β (ω)), second harmonic generation β (-2ω; ω,ω), electro-optic Pockel's effect β (-ω; ω,0), hyper-Rayleigh scattering coefficient (βHRS), second hyperpolarizability (γ (ω)), electric field-induced second harmonic generation γ(-2ω; ω, ω,0) electro-optic Kerr effect γ(-ω; ω,0,0), and nonlinear refractive indices (n2) were also studied. The highest dc-Kerr (2.69 × 1010 au) and EFISHG (3.69 × 109 au) values observed for K@Cubane along with large n2 (1.73 × 10−9 au) justify the large NLO response. These intriguing outcomes will be advantageous for promoting the possible utilization of designed complexes in the field of high-performance NLO materials.

In this study, based on two attractive energetic compounds pentazole (PZ) and tetraazacubane (TAC), a new family of high energy and high nitrogen compounds pentazolyltetraazacubanes were designed. Then, a different number of NH2 or NO2 groups were introduced into the system to further adjust the property. The structures, properties, and the structure-property relationship of designed molecules were investigated theoretically. The results showed that all nine designed compounds have extremely high heat of formation (HOF, 1226-2734 kJ/mol), good density (1.73–1.88 g/cm3), high detonation velocity (8.30–9.35 km/s), high detonation pressure (29.8–39.7 GPa) and acceptable sensitivity (ΔV: 41-87 Å3). These properties could be effectively positive adjusted by replacing one or two PZ rings by NH2 or/and NO2 groups, especially for the energy and sensitivity performance, which were increased and decreased obviously, respectively. As a result, two designed pentazolyltetraazacubanes were predicted to have higher energy and lower sensitivity than the famous high energy compound in use 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane, while two others have better combination property than 1,3,5-Trinitro-1,3,5-triazacyclohexane. In all, four new pentazolyltetraazacubanes with good combination performance were successfully designed by combining PZ with TAC, and the further property adjustment strategy of introducing a suitable amount of NH2/NO2 groups into the system. This work may help develop new cage energetic compounds.

On the basis of the energy conversion and storage, importance of chemical energy and charge transport, the objective of this research is study on cubane (C8H8; as an energetic molecule) and its molecular deformation by stepwise reduced states (C8H8n; n = 0 and − 1 to − 4). In this study, the molecule of cubane was optimized to obtain minimize molecular geometry and the electronic structure by the density functional theory (DFT, B3LYP) using 6-311G(d) basis set. Some important properties such as bond dissociation enthalpies, densities, frontier orbital (HOMO and LUMO) energies, thermodynamic parameters, natural bond orbital (NBO) populations, heat of formations and structural deformation parameters were calculated for C8H8n (n = 0 and − 1 to − 4). The calculated spectra of IR and NMR of the structures (C8H8n; n = 0 and − 1 to − 4) were also computed. The results of the DFT investigations revealed that this compound exhibit excellent performance in the oxidation process in its reduced form. [ABSTRACT FROM AUTHOR]

Metal ion interactions with nuclei acids and their constituents represent a multi-faceted and growing research field. This contribution deals with molecular recognition between synthetic purine 17 nucleosides and first-row transition metal complexes, with O- and/or N-amino chelators which are able to 18 engage in intra-molecular N-H···(N or O) and O-H···(N or O) interligand interactions. Crystals of these complexes can also display inter-molecular aromatic π-stacking and/or other non-conventional interactions. In this manuscript, we used 2-(2-aminoethoxy)ethanol (2aee) as a potential N,O(e),O(ol)-chelator for nickel(II). However, unexpectedly, the reaction between NiCl2, acyclovir (acv), and 2aee in methanol afforded parallelepiped apple-green crystals of [Ni(acv-H)(MeO)(H2O)]4·8H2O, (1) a tetranuclear molecule with an equimolar Ni(II):µ3-methanolate(1-):µ2-N7,O6-acyclovirate(1-) (acv-H) ratio. The µ2-N7,O6-(acv-H) metal-binding pattern (MBP) is unprecedented in terms of both its anionic and bridging roles. The single-crystal X-ray diffraction structure as well as thermogravimetric analysis and the (FT-IR +Vis-UV) spectra of 1 are reported. Theoretical density functional theory (DFT) calculations are used to analyse the antiparallel π-stacking interactions that govern the formation of self-assembled dimers in the solid state.

In an attempt to isolate boron-containing tri-niobium polychalcogenide species, we have carried out prolonged thermolysis reactions of [Cp*NbCl4] (Cp* = ɳ5-C5Me5) with four equivalents of Li[BH2E3] (E = Se or S). In the case of the heavier chalcogen (Se), the reaction led to the isolation of the tri-niobium cubane-like cluster [(NbCp*)3(μ3-Se)3(BH)(μ-Se)3] (1) and the homocubane-like cluster [(NbCp*)3(μ3-Se)3(μ-Se)3(BH)(μ-Se)] (2). Interestingly, the tri-niobium framework of 1 stabilizes a selenaborate {Se3BH}− ligand. A selenium atom is further introduced between boron and one of the selenium atoms of 1 to yield cluster 2. On the other hand, the reaction with the sulfur-containing borate adduct [LiBH2S3] afforded the trimetallic clusters [(NbCp*)3(μ-S)4{μ-S2(BH)}] (3) and [(NbCp*)3(μ-S)4{μ-S2(S)}] (4). Both clusters 3 and 4 have an Nb3S6 core, which further stabilizes {BH} and mono-sulfur units, respectively, through bi-chalcogen coordination. All of these species were characterized by 11B{1H}, 1H, and 13C{1H} NMR spectroscopy, mass spectrometry, infrared (IR) spectroscopy, and single-crystal X-ray crystallography. Moreover, theoretical investigations revealed that the triangular Nb3 framework is aromatic in nature and plays a vital role in the stabilization of the borate, borane, and chalcogen units.

Cubane, a hexahedral hydrocarbon, can be converted into an asymmetric molecule with a minimum of three substituents. The resulting chiral cubane can be used as a pharmacophore or a chiral ligand. Starting from the cubane carboxamide, the 1,2,3‐substituted compound was synthesized by sequential ortho‐metalation. The 1,3,5‐substituted compound was synthesized by combining site‐selective halogenation and halogen‐metal exchange and the resulting racemate was subjected to enantiomeric resolution by HPLC. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) approach was employed to investigate relaxation processes of each of pyrimidine nucleobases (NBs); cytosine (C), thymine (T) and uracil (U), at the Cubane Cluster Surface (CCS). The main idea was about providing a material for recognition of NBs, in which a nanostructure form of cubane (CCS) was first generated by optimization process. In the next step, relaxation processes of each of NBs at the surface were investigated to examine the function of such system for NBs recognition. The results indicated that the electronic based molecular properties could work as proper parameters for recognizing such molecular system, in which energy gap (EG) could be referred for the purpose. Measuring EG could help to recognize the complexes of CCS-C, CCS-T and CCS-U from each other. Strength of such complex formations was investigated using values of binding energy (BE); CCS-U > CCS-C > CCS-T. Total results of EG, BE and additional atomic scale properties indicated that the investigated CCS could work very well to recognize U as the characteristic NB of RNA. [ABSTRACT FROM AUTHOR]

A series of derivatives of nitroso-substituted cubane were designed through the substitution of hydrogen atoms by nitroso groups one by one. The heats of formation (HOFs) were calculated to explore the thermal stability. The bond dissociation energies (BDEs) and the bond orders of the trigger bonds were also investigated to explore the molecular stability kinetically. Furthermore, the steric effect was confirmed as the determinant of molecular stability for title molecules. To explore the detonation properties, the detonation pressure (P), the detonation velocity (D), the heat of detonation (Q), and the specific density (ρ) were calculated by using the empirical Kamlet-Jacobs (K-J) equations. To predict the sensitivity, the characteristic drop height (H50) is calculated. Based on our calculations, the octanitrosocubane is found with detonation parameters (D = 9.03 km/s, P = 36.96 GPa) better than that of RDX with enough stability. [ABSTRACT FROM AUTHOR]

A novel [Ni4(µ3-O)4] twisted cubane complex, Ni4Cl2(NN)2(ONN)2(NNO)2(H2O)2·2THF, was prepared from a crude mixture of three bidentate ligands. A mixture of ethyl 1-(hydroxymethyl)-3-methyl-1H-pyrazole-5-carboxylate (HONN) and ethyl 1-(hydroxyl-methyl)-5-methyl-1H-pyrazole-3-carboxylate (NNOH) were added to ethyl 3-methyl-1H-pyrazole-5-carboxylate (NNH) then mixed to NiCl2·6H2O solution under ambient conditions. Reaction progress was monitored via infrared and ultraviolet–visible spectroscopies and energy-dispersive X-ray spectroscopy was used to analyze the product. Reaction yields for cluster synthesis were very good. Single crystal structure determination for the cluster indicates a novel [Ni4(µ3-O)4] twisted cubane structure with octahedral geometry around each of the Ni(II) centers in Ni4Cl2(NN)2(ONN)2(NNO)2(H2O)2·2THF. The lattice is stabilized by hydrogen bonding and H– π stacking. Hirshfeld surface analysis (HSA) corroborates the single crystal structure determination results. The cluster displays significant thermal stability under open atmosphere conditions; it decomposes in three steps at high temperature. The cluster demonstrates promising results as a catalyst; it promoted the complete oxidation of catechol to o-Quinone in under mild conditions. [ABSTRACT FROM AUTHOR]

The remarkable structural and electronic properties of rigid non-conjugated hydrocarbons afford attractive opportunities to design molecular building blocks for both medicinal and material applications. The bridgehead positions provide the possibility to append diverse functional groups at specific angles and in specific orientations. The current review summarizes the synthetic development in CH functionalization of three rigid scaffolds namely: (a) cubane, (b) bicyclo[1.1.1]pentane (BCP), (c) adamantane. 1 Introduction 2 Cubane 2.1 Cubane Synthesis 2.2 Cubane Functionalization 3 Bicyclo[1.1.1]pentane (BCP) 3.1 BCP Synthesis 3.2 BCP Functionalization 4 Adamantane 4.1 Adamantane Synthesis 4.2 Adamantane Functionalization 5 Conclusions and Outlook [ABSTRACT FROM AUTHOR]

With the burgeoning interest in cage motifs for bioactive molecule discovery, and the recent disclosure of 1,4‐cubane‐dicarboxylic acid impact sensitivity, more research into the safety profiles of cage scaffolds is required. Therefore, the impact sensitivity and thermal decomposition behavior of judiciously selected starting materials and synthetic intermediates of cubane, bicyclo[1.1.1]pentane (BCP), and bicyclo[2.2.2]octane (BCO) were evaluated via hammer test and sealed cell differential scanning calorimetry, respectively. Iodo‐substituted systems were found to be more impact sensitive, whereas hydroxymethyl substitution led to more rapid thermodecomposition. Cubane was more likely to be impact sensitive with these substituents, followed by BCP, whereas all BCOs were unresponsive. The majority of derivatives were placed substantially above Yoshida thresholds—a computational indicator of sensitivity. [ABSTRACT FROM AUTHOR]

Nucleic acid aptamers selected through systematic evolution of ligands by exponential enrichment (SELEX) fold into exquisite globular structures in complex with protein targets with diverse translational applications. Varying the chemistry of nucleotides allows evolution of nonnatural nucleic acids, but the extent to which exotic chemistries can be integrated into a SELEX selection to evolve nonnatural macromolecular binding interfaces is unclear. Here, we report the identification of a cubane-modified aptamer (cubamer) against the malaria biomarker Plasmodium vivax lactate dehydrogenase (PvLDH). The crystal structure of the complex reveals an unprecedented binding mechanism involving a multicubane cluster within a hydrophobic pocket. The binding interaction is further stabilized through hydrogen bonding via cubyl hydrogens, previously unobserved in macromolecular binding interfaces. This binding mechanism allows discriminatory recognition of P. vivax over Plasmodium falciparum lactate dehydrogenase, thereby distinguishing these highly conserved malaria biomarkers for diagnostic applications. Together, our data demonstrate that SELEX can be used to evolve exotic nucleic acids bearing chemical functional groups which enable remarkable binding mechanisms which have never been observed in biology. Extending to other exotic chemistries will open a myriad of possibilities for functional nucleic acids. [ABSTRACT FROM AUTHOR]

The reactions of the phosphinoborane Ph2PBH2·NMe3 with Cu(I) halides [CuCl, CuBr, CuI] and [Cu(CH3CN)4BF4], respectively, were studied. Depending on the ratio of the reactants used, the former reaction allowed for the synthesis of eight neutral coordination compounds with the general formula [CunXn(Ph2PBH2·NMe3)m] (X = Cl, Br, I; n = 1, 2, 4, 5; m = 2, 4) (4–11). The latter reaction, however, led to the formation of the homoleptic complex [Cu(Ph2PBH2·NMe3)3][BF4] (13). The structures of the products 4–11 and 13 were compared to related complexes possessing the well‐known Ph3P ligand. All compounds were characterized by single crystal X‐ray structure analysis, multinuclear NMR spectroscopy, IR spectroscopy and mass spectrometry. [ABSTRACT FROM AUTHOR]

Density functional molecular orbital calculations are used to show the existence of two non-cubic isomeric structures of cubane and nitrated cubane. The isomers are shown to have no imaginary frequencies and are thus at a minimum on the potential energy surface. The calculations indicate the isomers are slightly more stable than the cubic structures. [ABSTRACT FROM AUTHOR]

The resurgence of interest in the hydrogen economy could hinge on the distribution of hydrogen in a safe and efficient manner. Whilst great progress has been made with cryogenic hydrogen storage or liquefied ammonia, liquid organic hydrogen carriers (LOHCs) remain attractive due to their lack of need for cryogenic temperatures or high pressures, most commonly a cycle between methylcyclohexane and toluene. Oxidation of methylcyclohexane to release hydrogen will be more efficient if the equilibrium limitations can be removed by separating the mixture. This report describes a family of six ternary and quaternary multicomponent metal–organic frameworks (MOFs) that contain the three‐dimensional cubane‐1,4‐dicarboxylate (cdc) ligand. Of these MOFs, the most promising is a quaternary MOF (CUB‐30), comprising cdc, 4,4′‐biphenyldicarboxylate (bpdc) and tritopic truxene linkers. Contrary to conventional wisdom that adsorptive interactions with larger, hydrocarbon guests are dominated by π–π interactions, here we report that contoured aliphatic pore environments can exhibit high selectivity and capacity for LOHC separations at low pressures. This is the first time, to the best of our knowledge, where selective adsorption for cyclohexane over benzene is witnessed, underlining the unique adsorptive behavior afforded by the unconventional cubane moiety. [ABSTRACT FROM AUTHOR]

Connecting two porphyrin units in a rigid linear fashion, without any undesired electron delocalization or communication between the chromophores, remains a synthetic challenge. Herein, a broad library of functionally diverse multi‐porphyrin arrays that incorporate the non‐traditional rigid linker groups cubane and bicyclo[1.1.1]pentane (BCP) is described. A robust, reliable, and versatile synthetic procedure was employed to access porphyrin‐cubane/BCP‐porphyrin arrays, representing the largest non‐polymeric structures available for cubane/BCP derivatives. These reactions demonstrate considerable substrate scope, from utilization of small phenyl moieties to large porphyrin rings, with varying lengths and different angles. To control conformational flexibility, amide bonds were introduced between the bridgehead carbon of BCP/cubane and the porphyrin rings. Through varying the orientation of the substituents around the amide bond of cubane/BCP, different intermolecular interactions were identified through single crystal X‐ray analysis. These studies revealed non‐covalent interactions that are the first‐of‐their‐kind including a unique iodine‐oxygen interaction between cubane units. These supramolecular architectures indicate the possibility to mimic a protein structure due to the sp3 rigid scaffolds (BCP or cubane) that exhibit the essential conformational space for protein function while simultaneously providing amide bonds for molecular recognition. [ABSTRACT FROM AUTHOR]

[Display omitted] Aromatic rings are critical core substructures in the majority of pharmaceutical compounds. There is much recent interest in replacing aromatic structures with saturated bioisosteres of benzene, which are generally fused or bridged ring systems. These bioisosteres often show improved solubility properties compared to benzene, and may also undergo fewer unwanted metabolic processes. One key reason why aromatic rings have proven so successful in drug design is their rigidity. This paper uses molecular dynamics simulations supported by crystallographic data to assess the rigidity of bicyclopentane and cubane ring systems as two of the most common benzene bioisosteres and compares this to benzene. Whilst a benzene ring is shown to be more flexible than these two bioisosteres in terms of its dihedral ring flexibility, substituents around the ring tend to behave in a much more similar way in both benzene and the bioisosteric systems. [ABSTRACT FROM AUTHOR]

A new crystal structure of catena-(bis((µ4-cubane-1,4-dicarboxylato)-(N-methyl-2-pyrrolidone)-zinc(II)) N-methyl-2-pyrrolidone solvate) (1) was prepared by solvothermal method. The crystal structure of the compound was analyzed by single-crystal X-ray diffraction. It has a P1 space group, with lattice parameters a = 10.7190(4) Å, b = 10.8245(5) Å, c = 10.8403(8) Å, a = 80.291(5)°, ß = 70.0015(5)°, γ = 77.531(4)°, V = 1147.97(12) ų. The secondary building units of 1 consist of 2 central Zn ions, coordinated by 4 carboxylate groups in a bis-monodentate way, forming a square planar configuration of Zn2(CO2)4, known as paddle-wheel units. The paddle-wheels are connected by cubane-1,4-dicarboxylic acid linkers at the edges, resulting in a two-dimensional coordination polymer with a square lattice (sql) underlying network topology. The axial sites of the zinc atoms are occupied by N-methyl-2-pyrrolidone molecules. In this new crystal structure the two-dimensional polymer planes are interstacked by weak dispersion bonds. The axial N-methyl- 2-pyrrolidone solvent molecules determine the distances of planar polymer planes. The thermal properties of this new structure were studied by thermogravimetry/mass spectrometry in inert atmosphere. It was found, that the organic linkers in the framework structure do not decompose below 200 °C. The stochiometry of the activated compound is Zn2[C8H6(COO)2]2(C5H9NO)2, as determined by thermogravimetry in oxidative atmosphere. [ABSTRACT FROM AUTHOR]

As infrared seeking technology evolves, threats are better able to distinguish defensive infrared (IR) flares from true targets. Spectrally matched flares, which generally employ carbon‐based fuels, are better able to decoy some advanced missiles by more closely mimicking the IR emission of the target. Cubane is a high‐energy carbon‐based scaffold which may be suitable for use as a fuel in spectrally matched flares. The enthalpy of formation and strain energy of a series of cubanes was predicted in silico, and their thermal and impact stability examined. All were found to undergo highly exothermic decomposition in sealed cell differential scanning calorimetry, and two cubanes subsequently underwent quantitative sensitiveness testing. Despite their F of I values being in the secondary explosive range, cubane‐1,4‐dicarboxylic acid (F of I=70) and 4‐carbamoylcubane‐1‐carboxylic acid (F of I=90) were identified as potentially useful fuels for pyrotechnic infrared countermeasure flare formulations. [ABSTRACT FROM AUTHOR]

A major challenge to the implementation of artificial photosynthesis (AP), in which fuels are produced from abundant materials (water and carbon dioxide) in an electrochemical cell through the action of sunlight, is the discovery of active, inexpensive, safe, and stable catalysts for the oxygen evolution reaction (OER). Multimetallic molecular catalysts, inspired by the natural photosynthetic enzyme, can provide important guidance for catalyst design, but the necessary mechanistic understanding has been elusive. In particular, fundamental transformations for reactive intermediates are difficult to observe, and well-defined molecular models of such species are highly prone to decomposition by intermolecular aggregation. Here, we present a general strategy for stabilization of the molecular cobalt-oxo cubane core (Co4O4) by immobilizing it as part of metal-organic frameworks, thus preventing intermolecular pathways of catalyst decomposition. These materials retain the OER activity and mechanism of the molecular Co4O4 analog yet demonstrate unprecedented long-term stability at pH 14. The organic linkers of the framework allow for chemical fine-tuning of activity and stability and, perhaps most importantly, provide "matrix isolation" that allows for observation and stabilization of intermediates in the water-splitting pathway. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • 3d-4f cubane-like complexes were reviewed. • The possible synthetic strategies of 3d-4f cubane-like complexes were reviewed. • The magnetic exchanges of 3d-4f cubane-like complexes were reviewed. • The magnetocaloric effect of 3d-4f cubane-like complexes were reviewed. • The single-molecule magnet properties of 3d-4f cubane-like complexes were reviewed. Abstract 3d-4f cubane-like complexes exhibit unique structural pattern, thus become a fascinating subclass of 3d-4f complexes. In this review, we first present the structural classification and the possible synthetic strategies towards this peculiar structure, then we focus on its magnetic properties. Inside a cubane core, spin carriers are forced to be near each other yielding significant d-d, d-f, and f-f magnetic exchanges which are summarized. As multinuclear complexes, 3d-4f cubane clusters could be applied for the magnetocaloric effect (MCE), especially with the isotropic MnII and GdIII ions. Then their single-molecule magnet (SMM) properties are described. We collect reported 3d-4f cubane complexes and attempt to demonstrate the correlations of magnetic exchange, MCE, and SMM properties. [ABSTRACT FROM AUTHOR]

While the coordination chemistry of monometallic complexes and the surface properties of extended metal particles are well understood, the control of metal nanocluster formation has remained challenging. The isolation of discrete metal clusters provides an especially rare snapshot at the nanoscale of cluster growth. The synthesis and full characterization of the first early‐transition‐metal alkynyl cubane and the first μ3‐alkynyl Mn3 motif are reported. [ABSTRACT FROM AUTHOR]

Graphical abstract We present density functional study of hydrocarbon [n]prismanes (n = 3–10) doped with Cl, F, OH, NO 2 and CH 3 radicals. Attaching of NO 2 radical results in the lowest values of HOMO-LUMO gaps. Highlights • We apply DFT to study functionalized carbon prismanes. • Energies, HOMO-LUMO gaps, dipole moments and polarizabilities are calculated. • Cl, F, OH, NO 2 and CH 3 functional groups are considered. • Isomers with adjacent radicals are less favorable. Abstract Density functional calculations of hydrocarbon prismanes C 2n H 2n (where n = 3–10) and their substituted derivatives are carried out to analyze their structures, binding energies and electronic properties. Five substituting radicals (F, Cl, CH 3 , OH, NO 2) are considered. The results indicate the different behavior of the prismanes by substitutions of hydrogen atoms with different radicals. Effective repulsion of substituting radicals on the pentaprismane cage is detected. The dependences of binding energies on number of substituted radicals demonstrate increasing or decreasing trends for different radicals. HOMO-LUMO gaps are slightly changed by substituting doping. All substituting reactions are found to be endothermal. Fluorination is more energetically feasible than other considered reactions. [ABSTRACT FROM AUTHOR]