1-adamantanecarboxylic Acid Research Articles

Guest-Mediated Reversal of the Tumbling Process in Phosphorus-Dendritic Compounds Containing β-Cyclodextrin Units: An NMR Study.

The conformational study of dendritic platforms containing multiple β-cyclodextrin (βCD) units in the periphery is relevant to determine the availability of βCD cavities for the formation of inclusion complexes in aqueous biological systems. In this work, we performed a detailed conformational analysis in D2O, via 1D and 2D NMR spectroscopy of a novel class of phosphorus dendritic compounds of the type P3N3-[O-C6H4-O-(CH2)n-βCD]6 (where n = 3 or 4). We unambiguously demonstrated that a functionalized glucopyranose unit of at least one βCD unit undergoes a 360° tumbling process, resulting in a deep inclusion of the spacer that binds the cyclodextrin to the phosphorus core inside the cavity, consequently limiting the availability of the inner cavities. In addition, we confirmed through NMR titrations that this tumbling phenomenon can be reversed for all βCD host units using a high-affinity guest, namely 1-adamantanecarboxylic acid (AdCOOH). Our findings have demonstrated that it is possible to create a wide variety of multi-functional dendritic platforms.

Synthesis of Novel N-(R)-2-(1-Adamantyl)-1H-Benzimidazole-5(6)- Carboxamide, Carbohydrazide and 1,3,4-Oxadiazole Derivatives

A novel series of benzimidazole-5(6)-carboxamide 3a-g, carbohydrazide 5a-e and 1,3,4- oxadiazole 6a-g derivatives bearing adamantane moiety were synthesized. The synthesis of benzimidazole heterocycle was performed by direct condensation/cyclization reaction of 1- adamantanecarboxylic acid with methyl 3,4-diaminobenzoate in Trimethylsilyl Polyphosphate (PPSE). The obtained Methyl 2-(1-adamantyl)-1H-benzimidazole-5(6)-carboxylate was converted to desired carboxamide and carbohydrazide derivatives in two different ways. In the first case, the synthesized ester after hydrolysis was converted to an acid chloride and subsequently coupled with different aromatic and heterocycle amines to give carboxamide derivatives. In the second case, treatment with hydrazine hydrate gave corresponding 2-(1-adamantyl)-1H-benzimidazole-5(6)-carbohydrazide which was coupled with some acyl chlorides to give appropriate carbohydrazide derivatives and with some aromatic acids to give 1,3,4-oxadiazole derivatives.

Anti-Seizure Activity of 1-Adamantane Carboxylic Acid in Common Experimental Seizure Models: Role of Benzodiazepine-GABAA Receptors.

Despite introduction of modern antiepileptic drugs, 30% of epileptic patients are still drug resistant. Remarkable three-dimensional spatial structure of 1-Adamantane carboxylic acid (AdCA), yet the simplicity of the molecule, makes AdCA a promising lead compound. Sedative/motor impairment and 24-h mortality rate of AdCA were determined in mice. Impact of AdCA on (1) threshold and occurrence of clonic seizures induced by pentylenetetrazole (PTZ) in mice, (2) incidence of tonic seizures induced by maximal electroshock (MES) in mice, and (3) incidence of generalized seizures and duration of evoked afterdischarges in amygdala-kindled rats, were determined. The role of benzodiazepine receptors in the AdCA effect on clonic seizure threshold was also assessed. AdCA showed sedative effect (median toxic dose [TD50] = 224.5 [190.2-289.9] mg/kg). Median lethal dose (LD50) = 805.5 (715.2–988.1) mg/kg was obtained for AdCA. The compound increased PTZ seizure threshold from 180 mg/kg (p < 0.05) and also inhibited the incidence of clonic seizures (ED50 = 256.3 [107.4-417.3] mg/kg). AdCA also decreased afterdischarge duration (p < 0.01) and the incidence of generalized seizures (ED50 < 50 mg/kg) in the kindled rats. However, AdCA did not protect mice against tonic seizures induced by MES. The benzodiazepine receptor antagonist flumazenil prevented the increase of seizure threshold by AdCA. AdCA possesses anticonvulsant activity in kindling and PTZ models through the activation of benzodiazepine/GABAA receptors with acceptable therapeutic index.

Structural Insights into the Host–Guest Complexation between β-Cyclodextrin and Bio-Conjugatable Adamantane Derivatives

Understanding the host–guest chemistry of α-/β-/γ- cyclodextrins (CDs) and a wide range of organic species are fundamentally attractive, and are finding broad contemporary applications toward developing efficient drug delivery systems. With the widely used β-CD as the host, we herein demonstrate that its inclusion behaviors toward an array of six simple and bio-conjugatable adamantane derivatives, namely, 1-adamantanol (adm-1-OH), 2-adamantanol (adm-2-OH), adamantan-1-amine (adm-1-NH2), 1-adamantanecarboxylic acid (adm-1-COOH), 1,3-adamantanedicarboxylic acid (adm-1,3-diCOOH), and 2-[3-(carboxymethyl)-1-adamantyl]acetic acid (adm-1,3-diCH2COOH), offer inclusion adducts with diverse adamantane-to-CD ratios and spatial guest locations. In all six cases, β-CD crystallizes as a pair supported by face-to-face hydrogen bonding between hydroxyl groups on C2 and C3 and their adjacent equivalents, giving rise to a truncated-cone-shaped cavity to accommodate one, two, or three adamantane derivatives. These inclusion complexes can be terminated as (adm-1-OH)2⊂CD2 (1, 2:2), (adm-2-OH)3⊂CD2 (2, 3:2), (adm-1-NH2)3⊂CD2 (3, 3:2), (adm-1-COOH)2⊂CD2 (4, 2:2), (adm-1,3-diCOOH)⊂CD2 (5, 1:2), and (adm-1,3-diCH2COOH)⊂CD2 (6, 1:2). This work may shed light on the design of nanomedicine with hierarchical structures, mediated by delicate cyclodextrin-based hosts and adamantane-appended drugs as the guests.

Determination of the anticancer properties of cis- and trans-diadamanthylcarboxylates of dirhenium(III)

The aim of the study. The aim of the work was to investigate in vivo anticancer activity of cis- and trans-diadamanthylcarboxylates of dirhenium(III) alone and together with cisplatin in form of nanobins.Materials and methods. Model of tumor growth, Guerin’s carcinoma; intraperitoneal administration of cisplatin, dirhenium(III) compounds in liposomes and of binary liposomes, containing both cytostatics; volumes and final weights of tumors were measured.Results. In vivo antitumor properties of two dirhenium(III) dicarboxylates with 1-adamantanecarboxylic acid moieties as ligands with cis- (I) and trans- (II) orientation of the carboxylic groups around a cluster fragment alone and together with cisplatin were presented; an attempt to understand differences in a possible mechanism of anticancer activity of the substances were undertaken. Antiradical and DNA-binding properties of I and II were the matter of consideration.Conclusions. Cis- and trans- compounds of dirhenium I and II had close antitumor activity in vivo with a little bit superiority of the cis- analog. Mechanisms of anticancer activity of I and II are different and may also include monofunctional adduct formation and subsequent interstrand cross-linking for the II substance, formation of protein-DNA cross-links, etc.

Antibacterial, Mutagenic Properties and Chemical Characterisation of Sugar Bush (Protea caffra Meisn.): A South African Native Shrub Species.

Protea caffra is used as a diarrhoeal remedy in South African herbal medicine, however, its pharmacological properties remain largely unknown. In the present study, extracts from different Protea caffra organs were screened against drug-sensitive and -resistant diarrhoeagenic pathogens using the microdilution assay (minimum inhibitory concentration, MIC). Twig extracts (70% methanol, MeOH) of the plant were purified and the resultant fractions screened for antibacterial properties (MIC). The chemical profiles of the fractions were determined by Gas Chromatography-Mass Spectrometry (GC-MS), while ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was used to quantify the phenolic acids in the plant. The mutagenic properties of bioactive extracts were assessed using the Ames test. The extracts demonstrated weak-moderate antibacterial properties (MIC: 0.3–0.6 mg/mL). A cold ethyl acetate fraction of MeOH twig extract exhibited significant antibacterial properties (MIC = 0.078 mg/mL) against Enterococcus faecalis. The presence of antibacterial compounds (1-adamantane carboxylic acid, heptacosanol, levoglucosan, nonadecanol) in the plant was putatively confirmed based on GC-MS analysis. Furthermore, UHPLC-MS/MS analysis revealed varying concentrations of phenolic acids (0.08–374.55 µg/g DW). Based on the Ames test, the extracts were non-mutagenic thereby suggesting their safety. To a certain degree, the current study supports the traditional use of Protea caffra to manage diarrhoea among local communities in South Africa.

Shape controlled assembly of carboxylic acids: formation of a binary monolayer by intercalation into molecular nanotunnels.

Binary self-assembled monolayers (SAMs) combining a Y-shaped aromatic carboxylic acid (1,3,5-benzenetribenzoic acid, H3BTB) and a cage-type alicyclic carboxylic acid (adamantane carboxylic acid, AdCA) were investigated by scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The SAMs, prepared by molecular adsorption from solution on Au substrates modified by underpotential deposition of Ag, exhibit a pronounced dependence of their structure on the assembly protocol. Exposing an H3BTB SAM to AdCA, the highly regular row structure of the native H3BTB layer persists and STM imaging does not show signs of AdCA adsorption. This is in striking contrast to the disordered arrangements of H3BTB and the presence of AdCA employing the inverted adsorption sequence or coadsorption of the two molecules. However, spectroscopic analysis of the H3BTB SAM exposed to AdCA reveals the presence also of the latter, suggesting that the AdCA molecules are hidden in the nanotunnels of the H3BTB monolayer. Direct evidence for the intercalation of AdCA is obtained by STM manipulation experiments which lay bare areas of AdCA molecules upon local removal of H3BTB. Surprisingly, these are densely packed and arranged into a highly ordered monolayer. Formation of such a compact AdCA layer is explained by expulsion of AdCA from the H3BTB nanotunnels of the surrounding intact mixed SAM, driven by release of stress in the nanotunnels built up when AdCA is intercalated.

New chemical agents based on adamantane-monoterpene conjugates against orthopoxvirus infections.

Currently, the spectrum of agents against orthopoxviruses, in particular smallpox, is very narrow. Despite the fact that smallpox is well controlled, there is, for many reasons, a real threat of epidemics associated with this or a similar virus. In order to search for new low molecular weight orthopoxvirus inhibitors, a series of amides combining adamantane and monoterpene moieties were synthesized using 1- and 2-adamantanecarboxylic acids as well as myrtenic, citronellic and camphorsulfonic acids as acid components. The produced compounds exhibited high activity against the vaccinia virus (an enveloped virus belonging to the poxvirus family), which was combined with low cytotoxicity. Some compounds had a selectivity index higher than that of the reference drug cidofovir; the highest SI = 1123 was exhibited by 1-adamantanecarboxylic acid amide containing the (-)-10-amino-2-pinene moiety. The produced compounds demonstrated inhibitory activity against other orthopoxviruses: cowpox virus (SI = 30-406) and ectromelia virus (mousepox virus, SI = 39-707).

Complexation Energies and Electronic-Structural Properties of Adamantane Derivatives: A DFT Study

This article is an investigation related to the complexation energies, binding abilities, frontier molecular orbital’s energy gaps and dipole moments on dimeric forms of 1-adamantanol, 1-adamantanemethylamine and 1-adamantanecarboxylic acid as the adamantane derivatives. All the optimizations, counterpoise corrections and complexation energy computations have been achieved by density functional theory with B3LYP and WB97XD functionals. In all counterpoise calculations have been used the empirical dispersion method with B3LYP and WB97XD for non-covalent interactions. The more favorable complexation energies have been obtained by B3LYP with the addition of dispersion correction. In addition, the images mapped with total density and electrostatic potential have been obtained in this study.

Diamondoids are not forever: microbial biotransformation of diamondoid carboxylic acids.

SummaryOil sands process‐affected waters (OSPW) contain persistent, toxic naphthenic acids (NAs), including the abundant yet little‐studied diamondoid carboxylic acids. Therefore, we investigated the aerobic microbial biotransformation of two of the most abundant, chronically toxic and environmentally relevant diamondoid carboxylic acids: adamantane‐1‐carboxylic acid (A1CA) and 3‐ethyl adamantane carboxylic acid (3EA). We inoculated into minimal salts media with diamondoid carboxylic acids as sole carbon and energy source two samples: (i) a surface water sample (designated TPW) collected from a test pit from the Mildred Lake Settling Basin and (ii) a water sample (designated 2 m) collected at a water depth of 2 m from a tailings pond. By day 33, in TPW enrichments, 71% of A1CA and 50% of 3EA was transformed, with 50% reduction in EC20 toxicity. Similar results were found for 2 m enrichments. Biotransformation of A1CA and 3EA resulted in the production of two metabolites, tentatively identified as 2‐hydroxyadamantane‐1‐carboxylic acid and 3‐ethyladamantane‐2‐ol respectively. Accumulation of both metabolites was less than the loss of the parent compound, indicating that they would have continued to be transformed beyond 33 days and not accumulate as dead‐end metabolites. There were shifts in bacterial community composition during biotransformation, with Pseudomonas species, especially P. stutzeri, dominating enrichments irrespective of the diamondoid carboxylic acid. In conclusion, we demonstrated the microbial biotransformation of two diamondoid carboxylic acids, which has potential application for their removal and detoxification from vast OSPW that are a major environmental threat.

Self-healing thiol-ene networks based on cyclodextrin-adamantane host-guest interactions

The reactions of β-cyclodextrin, pentaerythritol propoxylate and 1-adamantanecarboxylic acid with allyl bromide in the presence of basic salts generated their allylated products (ACD, APEP and AAd, respectively). The thiol-ene photopolymerizations of these allylated compounds and pentaerythritol tetrakis(3-mercaptopropionate) (S4P) produced thiol-ene network films (ACD-S4P, ACD-APEP-S4P, ACD-AAd-S4P, APEP-AAd-S4P and ACD-APEP-AAd-S4P). The FT-IR and gel fraction measurements of the photo-cured films revealed that almost all the thiol and allyl groups were consumed, and polymer networks were certainly formed. Glass transition temperatures (0.5 and 0.3 °C) of ACD-S4P and ACD-AAd-S4P were higher than those (−9 to −15 °C) of other films incorporating APEP. The tensile strength and modulus of ACD-S4P were much higher than those of the films incorporating APEP or AAd. Only the films incorporating both ACD and AAd possessed the self-healing property. ACD-AAd-S4P showed a higher tensile strength and modulus than ACD-APEP-AAd-S4P did. ACD-AAd-S4P was healed twice at 80 °C and only once at room temperature. ACD-APEP-AAd-S4P was healed only once at 80 °C. The maximum healing efficiency was 85% for tensile modulus of ACD-AAd-S4P.

An Efficient and Practical Method for the Synthesis of Saxagliptin Intermediate 2-(3-Hydroxy-1-adamantane)-2-oxoacetic Acid and Its Optimization

A mild and relatively simple way for preparation of 2-(3-hydroxy-1-adamantane)-2-oxoacetic acid (I) was reported. It was prepared from 1-adamantanecarboxylic acid (II) via sulfuric acid/nitric acid to get 3-hydroxy-1-adamantanecarboxylic acid (III); treated with the one-pot method through acylation, condensation, and decarboxylation to obtain 3-hydroxy-1-acetyladamantane (IV); and finally oxidized by potassium permanganate (KMnO4) to get the target compound (I). The overall yield was about 60%, which provides a new idea for commercial production of saxagliptin intermediate.

Solvothermal synthesis, structural characterization, DFT and magnetic studies of a dinuclear paddlewheel Cu(II)-metallamacrocycle

Abstract A new dinuclear paddlewheel Cu(II)-metallamacrocycle with the formula [{Cu2(3-bpoba)(adman)4}·3DMF]2 (1) (where, 3-bpoba is 4,4′-oxybis(N-(pyridin-3-yl)benzamide); adman is 1-adamantanecarboxylic acid), has been synthesized using the solvothermal protocol. A single-crystal X-ray analysis reveals that 1 exhibit a dinuclear paddlewheel metallamacrocycle architecture, where the co-ligand adman is playing a crucial role in the formation of metallacyclic structure. TGA analysis suggests that 1 is stable up to 250 °C. Density Functional Theory (DFT) has been employed to calculate the equilibrium geometry of the complex as isolated species in the gaseous phase. The structural analysis was complemented by additional spectroscopic studies and Hirshfeld surface analysis. Variable temperature magnetic susceptibility measurements on 1 show a strongly coupled magnetic dimer (J = −538(2) K) as expected for a classic Cu-paddlewheel structure.

Facile Synthesis of 3-(Azol-1-yl)-1-adamantanecarboxylic Acids-New Bifunctional Angle-Shaped Building Blocks for Coordination Polymers.

For the first time, orthogonally substituted azole-carboxylate adamantane ligands were synthesized and used for preparation of coordination polymers. The angle-shaped ligands were prepared by the reaction of 1-adamantanecarboxylic acid and azoles (1H-1,2,4-triazole, 3-methyl-1H-1,2,4-triazole, 3,5-dimethyl-1H-1,2,4-triazole, 1H-tetrazole, 5-methyl-1H-tetrazole) in concentrated sulfuric acid. Variation of the solvent and substituents in azole rings allowed to prepare both 1D and 2D copper(II) and nickel(II) coordination polymers, [Cu2(trzadc)4(H2O)0.7]∙DMF∙0.3H2O, [Cu(trzadc)2(MeOH)]∙MeOH, [Ni(trzadc)2(MeOH)2] and [Cu2(mtrzadc)3(MeOH)]+NO3– (trzadc-3-(1,2,4-triazol-1-yl)-adamantane-1-carboxylic acid; mtrzadc-3-(3-methyl-1,2,4-triazol-1-yl)-adamantane-1-carboxylic acid) which were structurally characterized by single crystal X-ray diffraction. Complex [Cu(trzadc)2(MeOH)]∙MeOH was shown to act as a catalyst in the Chan-Evans-Lam arylation reaction.

Photodegradation of naphthenic acids induced by natural photosensitizer in oil sands process water

Utilization of renewable solar energy driven advanced oxidation processes for oil sands process water (OSPW) remediation has received extensive attention. Naturally existing inorganic photosensitizer in OSPW was investigated in this work to provide information about the application of indirect photolysis treatment of organic contaminants in OSPW. OSPW and OSPW organic fraction were exposed under UV irradiance with fluence of 10 J/cm2 to investigate the effect of OSPW inorganic fraction (OSPW-IF) on the non-catalytic photolysis of naphthenic acids (NAs) in OSPW. The results indicated that the inorganic fraction in OSPW enhanced the photodegradation of NAs, with 24.3% of total NA removal in OSPW, while only 12.4% of total NAs were removed in OSPW organic fraction. Moreover, the photodegradation of 1-adamantanecarboxylic acid (ACA) dissolved in OSPW-IF or carbonate buffer was conducted to verify the enhanced photodegradation of NAs by OSPW-IF. The results showed that 30.9% of ACA was removed in the OSPW-IF, while no ACA degradation was observed in carbonate buffer after 60 min of UV exposure, indicating that the OSPW-IF induced the photodegradation of ACA. In addition, nitrate was identified to be the photosensitizer in OSPW-IF responsible for the indirect photolysis of ACA. In the presence of nitrate, both hydroxyl radicals (•OH) and reactive nitrogen species were generated, where •OH was the dominant reactive species that contributed to the degradation of ACA. Ten possible by-products ranging from single to multiple hydroxyl, nitroso, nitro and carbonyl substituted products were proposed to be produced from the nitrate-induced photodegradation process through three different pathways. This study demonstrated that the photolysis of NAs in OSPW due to the presence of natural photosensitizers and nitrate could act as a natural photosensitizer for the remediation of OSPW by the photo-oxidation process.

Novel Inhibitors of DNA Repair Enzyme TDP1 Combining Monoterpenoid and Adamantane Fragments.

The DNA repair enzyme tyrosyl-DNA-phosphodiesterase 1 (TDP1) is a current inhibition target to improve the efficacy of cancer chemotherapy. Previous studies showed that compounds combining adamantane and monoterpenoid fragments are active against TDP1 enzyme. This investigation is focused on the synthesis of monoterpenoid derived esters of 1-adamantane carboxylic acid as TDP1 inhibitors. New esters were synthesized by the interaction between 1-adamantane carboxylic acid chloride and monoterpenoid alcohols. The esters were tested against TDP1 and its binding to the enzyme was modeling. 13 Novel ester-based TDP1 inhibitors were synthesized with yields of 21-94%; of these, nine esters had not been previously described. A number of the esters were found to inhibit TDP1, with IC50 values ranging from 0.86-4.08 µM. Molecular modelling against the TDP1 crystal structure showed a good fit of the active esters in the catalytic pocket, explaining their potency. A non-toxic dose of ester, containing a 3,7- dimethyloctanol fragment, was found to enhance the cytotoxic effect of topotecan, a clinically used anti-cancer drug, against the human lung adenocarcinoma cell line A549. The esters synthesized were found to be active against TDP1 in the lower micromolar concentration range, with these findings being corroborated by molecular modeling. Simultaneous action of the ester synthesized from 3,7-dimethyloctanol-1 and topotecan revealed a synergistic effect.

Biodegradation of 1-adamantanecarboxylic acid by algal-bacterial microbial communities derived from oil sands tailings ponds

Oil sands tailings ponds store millions of litres of water and solid wastes generated during the surface mining of oil sands deposits in Alberta, Canada. As government regulations mandate the ultimate reclamation of tailings ponds, toxic compounds within tailings, such as naphthenic acids, must be treated. Bioremediation holds promise as a cost-effective approach to treat compounds such as naphthenic acids in tailings ponds. While previous research showed that microorganisms (mainly bacteria) indigenous to tailings can biodegrade such compounds, most studies have used simple model compounds that do not always reflect the naphthenic acid composition of tailings ponds. Here, we assessed the ability for photosynthetic microbial communities derived from tailings ponds to biodegrade 1-adamantanecarboxylic acid, a model diamondoid naphthenic acid that has been detected in tailings ponds water and that has known recalcitrance and toxicity. Over the course of 90 days, the microbial communities were able to degrade this diamondoid NA by up to ~80% compared to controls. 16S and 18S rRNA gene sequencing showed that algae dominated the enrichments, with members of the order Chlorellales and the genus Acutodesmus (Scenedesmus) comprising ~90% of the relative sequence abundance. These data suggest that such algae played a key role in the biodegradation of 1-adamantanecarboxylic acid. This study demonstrates that algal communities present in oil sands tailings ponds have the potential to serve as remedial agents to treat the recalcitrant and toxic naphthenic acids in oil sands tailings ponds.

Molecular Logic as a Means to Assess Therapeutic Antidotes.

An emerging direction in the area of molecular logic and computation is developing molecular-scale devices that can operate in complex biological environments, such as within living cells, which are beyond the reach of conventional electronic devices. Herein we demonstrate, at the proof-of-principle level, how concepts applied in the field of molecular logic gates can be used to convert a simple fluorescent switch (YES gate), which lights up in the presence of glutathione s-transferase (GST), into a medicinally relevant INHIBIT gate that responds to both GST and beta-cyclodextrin (β-CD) as input signals. We show that the optical responses generated by this device indicate the ability to use it as an enzyme inhibitor, and more importantly, the ability to use β-CD as an “antidote” that prevents GST inhibition. The relevance of this system to biomedical applications is demonstrated by using the INHIBIT gate and β-CD to regulate the growth of breast cancer cells, highlighting the possibility of applying supramolecular inputs, commonly used to control the fluorescence of molecular logic gates, as antidotes that reverse the toxic effect of chemotherapy agents. We also show that the effect of β-CD can be prevented by introducing 1-adamantanecarboxylic acid (Ad-COOH) as an additional input signal, indicating the potential of obtaining precise, temporal control over enzyme activity and anticancer drug function.

THE INTERACTION OF DIRHENIUM(III) CLUSTER COMPOUNDS WITH SUCCINIC ACID

Complex compounds of dirhenium(III) with bridge carboxylates and halide ligands show various types of bioactivity, and the entry into the internal coordination sphere of the central “atom”- complexing the ligands that have their own physiological activity may extend the range of useful properties of dirhenium(III) complex compounds. From this perspective development the methods of synthesis of dirhenium(III) complex compounds with such ligands and determination of their structure are promising. In this work the interaction (NBu 4 ) 2 Re 2 Cl 8 with succinic acid under different conditions was investigated. As a result of these experiments, the method of synthesis of cis-tetrachlorodi-μ-ethane-1,2-dicarboxylates of dirhenium(III) (axial ligands are DMSO or DMF) in mixture of organic solvents with heating under inert atmosphere was developed. These compounds were synthesized and isolated in the individual state, their spectral properties were investigated. The composition and structure of synthesized compounds were confirmed by IR spectroscopy, NMR spectroscopy at 1Н, 13С and EAS. The single absorption maximum at 16 130 cm-1, which corresponds to the δ - δ* electron transition for cis-tetrachlorodi-μ-carboxylates of dirhenium(III), is present in the EAS visible region of the complex compounds solution. In the IR spectrum the intense, weakly split band at 1428 cm-1 is observed. This band corresponds to the stretching vibration νas(СО) of the coordinated carboxylate group and confirms the addition of succinic acid to the cluster fragment Re 2 6+ . Also, the reaction of the same starting compounds under melting condition and inert atmosphere lead to formation of dirhenim(III) tetra-μ-carboxylate with ethan-1,2-dicarboxylic acid. The complex compound was isolated in solid state, its composition and structure were proved. The interaction of Re 2 (HOOC(CH 2 ) 2 COO) 4 Cl 2 with 1-adamantanecarboxylic acid lead to the complete replacement of the equatorial ligands on adamantanecarboxylates groups with the preservation of the structural type of dirhenium(III) tetra-μ-carboxylate.

Symmetry breaking and switchable thermal dielectric behaviors triggered by order-disorder phase transition in a neutral co-crystallized organic adduct

Reversible crystal state structural phase transitions molecular materials without metal have been received increasing interest recently. Here we successfully synthesized a novel ternary neutral co-crystallized organic adduct hexamethylenetetramine·1-adamantane carboxylic acid·chloroform, 1, which accompanies with an interesting reversible phase transition close to the zero temperature (263 K). We confirmed this reversible phase transition by its switchable thermal dielectric behaviors and unit cell constants anomalies around the phase transition temperature (Tc). X-ray single crystal diffraction analysis above (1-RTP) and below (1-LTP) Tc suggests that the order-disorder motion from the adamantane ring in 1-adamantane carboxylic acid triggered the reversible phase transition.