Cymantrene Derivatives Research Articles

2-Imidazoline Nitroxide Derivatives of Cymantrene.

The 2-imidazoline nitroxide derivatives of cymantrene-2-(η5-cyclopentadienyl)tricarbonylmanganese(I)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (NNMn) and 2-(η5-cyclopentadienyl)tricarbonylmanganese(I)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-1-oxyl (INMn) were synthesized. It was shown that NNMn and INMn exhibit a sufficiently high kinetic stability both in solids and in solutions under normal conditions. Their structural characteristics, magnetic properties and electrochemical behavior are close to Re(I) analogs. This opens the prospect of using paramagnetic cymantrenes as prototypes in the design of Re(I) half-sandwiched derivatives for theranostics, where therapy is combined with diagnostics by magnetic resonance imaging due to the contrast properties of nitroxide radicals.

Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, ul. Vavilova 28, Moscow, 119991 Russia

The article describes the main properties and applications of tri- and dicarbonyl derivatives of cymantrene bearing a C=O donor fragment capable of coordinating with manganese atoms. Recent reports of different research groups, including our, show that these compounds can be of interest for the creation of photosensitive smart materials owing to the possibility of formation of photochromic systems between hemilabile di- and tricarbonyl complexes. The properties of these complexes of cymantrene with ketone, amide, and carbamate groups of both monomeric and cascade structures are considered.

Hemilabile Properties of Sulfur‐Containing Cymantrene Derivatives

AbstractSulfur‐containing cymantrene derivatives having one or two organometallic moieties were studied by NMR, IR, UV/Vis spectroscopic methods and CVA under irradiation conditions. Photolysis of compounds 1–3 leads to the formation of rare 4‐membered chelates 4, 5 and 8. In the presence of external ligand (L), dissociation of the Mn−S bond occurred to form new dicarbonyl complexes with the Mn−L bond, which demonstrates the hemilabile character of the chelates obtained. The results were confirmed by DFT calculations. CVA method showed manganese oxidation potential value increased in the case of dicarbonyls (1313 mV for 4) as compared to that of tricarbonyls (1067 mV for 1).

Cymantrene Derivatives Containing Imino Groups: Spectral and Photochemical Properties

The investigation of a photochemical behavior of imino derivatives of cymantrene reveals a possibility of formation of four-membered hemilabile chelate complexes. In the presence of external ligands, such as CO, MeCN, or PPh3, the ligand exchange between imino groups at the Mn atom in dicarbolyl chelates and the external ligand is observed. It is shown that MeCN or PPh3 can be substituted for CO under dark conditions, resulting in intermolecular photochromic systems between tricarbonyl complexes and dicarbonyl derivatives with MeCN and PPh3 ligand, respectively.

Synthesis of Sulfur-Containing Cymantrene Derivatives Having Potential Photo- and Electrochemical Properties

With the aim of preparing of sulfur-containing derivatives of cymantrene, the hydrolysis of isothiouronium salts of alkylcymantrenes was studied under various conditions as well as subsequent chemical transformations of hydrolysis products. It was found that alkylcymantrenylthiols can be prepared either by hydrolysis of isothiouronium salts under the action of NaOH in a EtOH-acetone (4 : 1) mixture for 2 h or by the reduction of the corresponding disulfides by LiAlH4 formed in the course of this reaction in good yield for 6 h. Electrochemical properties of disulfides Cym(CHCH3)SS(CHCH3)Cym (Cym = C5H4Mn(CO)3) in solution before and after irradiation with a Hg lamp at λ365 nm were studied. The structures of the compounds were established by the X-ray analysis (CymCH(CH3)SSCH(CH3)Cym (I) (CIF file CCDC no. 1921952) and CymCH2SCH2Cym (II) (CIF file CCDC no. 1921953)).

Thioureido Cymantrene Derivatives: Synthesis and Photochromic Properties

Photolysis of thioureido derivatives of cymantrene in solution and solvent-free affords stable six-membered dicarbonyl chelates due to coordination of sulfur of the C═S group to manganese. The proc...

Synthesis and Photochemical Study of Thiazolidine Derivatives of Cymantrene and the Corresponding Dicarbonyl Chelates

AbstractIsomeric 4,5‐dihydro‐2‐[(cymantrenylmethyl)thio]thiazole (1) and 3‐(cymantrenylmethyl)‐1,3‐thioazolidine‐2‐thione (2) were synthesized and photochemical behavior and spectral characteristics of tricarbonyl and dicarbonyl complexes were studied. Irradiation of compounds 1 and 2 results in the formation of stable chelates due to coordination of manganese to the donor nitrogen and sulfur atoms of the thiazolidine substituent. Photolysis is accompanied with a colour change and the corresponding changes in the UV/Vis spectra depending on the solvent used. In the presence of CO, the dicarbonyl chelates enter the dark reaction to give the parent tricarbonyl complexes thus forming intermolecular photochromic systems. Photolysis of the dicarbonyl chelate 5 gives the isomeric chelate 6, which in the course of the dark isomerization transforms into complex 5. Chelates 5 and 6 form an intramolecular photochromic pair.

SYNTHESIS OF CYCLOCARBINOL AND CYCLOCARBINOLATE DERIVATIVES OF CYMANTRENE AND THEIR ANTI-SMOKE EFFECTIVENESS FOR DIESEL FUELS

The results of the development of synthesis technique of cyclocarbinol derivatives of cymantrene and the production of relevant barium cyclocarbinolate metal complexes – new, advanced anti-smoke additives were presented. Comparative data on the anti-smoke effectiveness of synthesized compounds and known antismoke additives for diesel fuels were also presented. Established, results of the development of a single-stage synthesis method of cyclocarbinol derivatives of cymantrene can be assumed as a basic process for producing high-effective anti-smoke additives to diesel fuels that comply with the requirements of ecology in operation of diesel vehicles.

Synthesis of Azaheterocyclic Cymantrene Derivatives

The reduction of acetylcymantrene with sodium tetrahydridoborate gave cymantrenylethanol which was acylated with 4,5-dichloroisothiazole- and 5-(4-methylphenyl)isoxazole-3-carbonyl chlorides to obtain esters containing a 1,2-thia(oxa)zole fragment. The condensation of acetylcymantrene with 5-arylisoxazole-3- carbaldehydes, (5-arylisoxazol-3-yl)methoxybenzaldehydes (Ar = Ph, 4-Tol), and 4,5-dichloroisothiazole-3- carbaldehyde afforded the corresponding (E)-3-(azol-3-yl)-1-cymantrenylprop-2-en-1-ones. The resulting α,β- unsaturated ketones reacted with semicarbazide hydrochloride and thiosemicarbazide to produce substituted 4,5-dihydro-1H-pyrazole-1-carboxamides and -1-carbothioamides, and their reaction with hydroxylamine hydrochloride led to the formation of 4,5-dihydroisoxazoles containing cymantrene and 1,2-azole fragments. Heterocyclization of azolylcymantrenylpropenones with guanidine gave 2-aminopyrimidine derivatives, and dihydropyrimidine-2-thiones were obtained by their reaction with thiourea.

Cymantrenyl-Nucleobases: Synthesis, Anticancer, Antitrypanosomal and Antimicrobial Activity Studies.

The synthesis of four cymantrene-5-fluorouracil derivatives (1–4) and two cymantrene-adenine derivatives (5 and 6) is reported. All of the compounds were characterized by spectroscopic methods and the crystal structure of two derivatives (1 and 6), together with the previously described cymantrene-adenine compound C was determined by X-ray crystallography. While the compounds 1 and 6 crystallized in the triclinic P-1 space group, compound C crystallized in the monoclinic P21/m space group. The newly synthesized compounds 1–6 were tested together with the two previously described cymantrene derivatives B and C for their in vitro antiproliferative activity against seven cancer cell lines (MCF-7, MCF-7/DX, MDA-MB-231, SKOV-3, A549, HepG2m and U-87-MG), five bacterial strains Staphylococcus aureus (methicillin-sensitive, methicillin-resistant and vancomycin-intermediate strains), Staphylococcus epidermidis, and Escherichia coli, including clinical isolates of S. aureus and S. epidermidis, as well as against the protozoan parasite Trypanosoma brucei. The most cytotoxic compounds were derivatives 2 and C for A549 and SKOV-3 cancer cell lines, respectively, with 50% growth inhibition (IC50) values of about 7 µM. The anticancer activity of the cymantrene compounds was determined to be due to their ability to induce oxidative stress and to trigger apoptosis and autophagy in cancer cells. Three derivatives (1, 4 and 5) displayed promising antitrypanosomal activity, with GI50 values in the low micromolar range (3–4 µM). The introduction of the 5-fluorouracil moiety in 1 enhanced the trypanocidal activity when compared to the activity previously reported for the corresponding uracil derivative. The antibacterial activity of cymantrene compounds 1 and C was within the range of 8–64 µg/mL and seemed to be the result of induced cell shrinking.

Synthesis, structure and DFT study of asymmetrical NHC complexes of cymantrene derivatives and their application in the dehydrogenative dimerization reaction of thiols

Asymmetrical NHC complexes of cymantrene and methylcymantrene have been synthesised through the photochemical substitution of carbonyl ligands in the presence of the imidazol-2-ylidene salts. The carbene substituents have been varied between compact (L1) and bulky (L2 and L3) substituents to produce an array of differently sized carbene ligands. The solid state crystal structures of three of the complexes confirmed the bonding pattern of the ligand towards available metal centres and an in-depth DFT study provided insight into electronic and steric aspects. Application of the Extended Transition State coupled with Natural Orbitals for Chemical Valence (ETS-NOCV) energy decomposition technique indicated various NOCV channels for each Mn–L bond (L = 3-ethyl-1-methylimidazolylidene carbene, triphenylphosphine or acetonitrile), describing the density and energy changes of specific (σ and π) attributes of each bond. N-heterocyclic carbenes of cymantrene derivatives and their triphenylphosphine-substituted analogue are equivalent σ-donors, with 53% and 56%, respectively, of the total binding energy originating from σ-donation. However, NHC complexes show considerably less π character in the metal-carbene bond. Hydrogen interactions in the NHC complexes were also identified in the ETS-NOCV calculations and provided quantification of the hydrogen interactions witnessed in the solid state structures. Calculated Wiberg bond indices, bond dissociation enthalpies, percentage buried volumes and percentage sigma and pi-bonding characteristics quantified the bonding and electronic aspects of the ligand-metal interactions within the complex.

Kinetic Resolution of Planar-Chiral (η5-Bromocyclopentadienyl)manganese(I) Complexes by Molybdenum-Catalyzed Asymmetric Ring-Closing Metathesis

Kinetic resolution of racemic planar-chiral (η5-1-alkenyl-2-bromocyclopentadienyl)manganese(I) complexes 1 was realized by the molybdenum-catalyzed asymmetric ring-closing metathesis. While vinyl-Cp derivative 1a was resolved in excellent enantioselectivity with the krel values of up to 127, the selectivity in the ARCM reaction of allyl-Cp derivative 1b was modest (krel = 3.0). ARCM product 2a, which was obtained in an enantiomerically pure form by the two successive ARCM reactions or recrystallization of the enantiomerically enriched products, was found to be a versatile synthetic precursor to various planar-chiral cymantrene derivatives.

Synthesis and properties of quinazoline derivatives containing cymantrenyl group

The synthesis of new quinazoline derivatives with 2,3- and 4-positioned cymantrenyl fragment is described. Alkylation of 2-substituted quinazolin-4-ones with cymantrenylalkyl bromides on using K2CO3, potassium tert-butoxide, and sodium hydride as bases has been studied. It is established for the first time that condensation of 2-methylquinazolin-4-ones with aldehydes can cause elimination of the substituent at the nitrogen atom in position 3. The new cymantrene derivatives possess fluorescence properties.

Azinyl derivatives of ferrocene and cymantrene. Synthesis and properties

In the present review comparative data concerning various synthetic approaches and methodologies used in the series of ferrocene and cymantrene derivatives to create various materials, namely, catalytic systems, sensory and other molecular devices, polymers as well as physiologically active substances, for the period from 2000 till 2016 are given. Aspects of practical application of the above compounds are also considered.

Synthesis and Spectroscopic Studies of the Photochromism of Bifunctional Derivatives of Cymantrene in Solution and without Solvent

Four monosubstituted cymantrene derivatives (5–8) containing two functional groups (allyl and amide) in a dendritic substituent were synthesized. The irradiation of these compounds with an Hg lamp in solution and under solvent‐free conditions gives two types of dicarbonyl chelates with Mn–olefin or Mn–amide coordination bonds. Olefin chelates (19 and 21) were isolated for the first time, and they undergo reverse photochemical intramolecular isomerization to the amide chelates in solution and as pure liquids. For the first time, it was shown that the photochromism of cymantrene functional derivatives can be observed without the use of a solvent.

Dicarbonyl chelates from 1-cymantrenylalkylamides with the dendrite structure: formation, photochromism, and kinetics of dark reaction with carbon monoxide

Photolysis of carboxamides of the dendrite structure with aminomethyland 1-aminoethylcymantrenes leads to the formation of six-membered dicarbonyl chelates with the Mn—O bond which are stable in solutions. The chelates in the reversed dark reaction with carbon monoxide give the starting tricarbonyl complexes. The formation of the chelates and their dark reaction are accompanied by the reversible change of color by the compounds. The rate determining step of the thermal reaction of chelates with CO is a chelate ring opening with the ligand substitution by the SN1 mechanism. A possibility of solvent-free photoinduced ligand-exchange reaction in a number of cymantrene derivatives was demonstrated.

Synthesis and photochemical properties of 1,2,3-triazoles containing (cyclopentadienyl)(tricarbonyl)manganese

The photochemical behavior of a series of monoand bifunctional derivatives of cymantrene with a triazole ring in the substituent was studied. It was shown for the first time that triazoles and triazolium salts can function as efficient n-donor ligands in the formation of cyclopentadienyl manganese dicarbonyl chelates.

Orientation in the metalation of amide, carbamate, ureido, and allylic derivatives of cymantrene

The orientation in the metalation of monosubstituted carbamate-, amide-, ureido-, and allyl-containing derivatives of cymantrene was determined for the first time. The data obtained open up a synthetic route to polyfunctional 1,2- and 1,3-disubstituted cymantrenes. They can serve as the starting materials for the preparation of chelate complexes of (dicarbonyl)-(cyclopentadienyl)manganese, which hold promise as novel organometallic photochromes. A method for the synthesis of earlier unknown chiral derivatives of cymantrene with a quaternary carbon atom in position 1 of the side chain was proposed.

Heterocyclic cymantrene derivatives in the radical polymerization of methyl methacrylate

Heterocyclic cymantrene derivatives in the radical polymerization of methyl methacrylate

Supramolecular interactions in the structures of carboxylate derivatives of cymantrene and single-charged cations

The ability of cymantrenecarboxylate derivatives to form supramolecular structures has been studied for ten newly prepared derivatives of cymantrenecarboxylic acid (η5-C5H4COOH)Mn(CO)3 and two new derivatives of β-cymantrenoylpropionic acid (η5-C5H4CO(CH2)2COOH)Mn(CO)3 with cations of alkaline metals and protonated polytopic nitrogen bases of various geometries. It has been shown that structures of this kind (two- and three-dimensional) are formed owing to specific properties of the cymantrene moiety, i.e., its ability to coordinate metal ions via CO groups (to form isocarbonyl bridges) and to form CO⋯H hydrogen bonds, but in most of the cases the type of the structure is determined by the cation. In case of Li cymantrenecarboxylate complex the formation of hexameric molecules having a cavity was found. The crystal and molecular structure of cymantrenecarboxylic acid has been described for the first time.