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(A) Synthetic route to 9,9′,12,12′-tetraethyl-1,1′-bis(o-carborane) (7), syntheses of 5 and 6 from ref. 6k. (B) X-ray crystal structure of 8 (CCDC 1446944) with thermal ellipsoids drawn at 50% probability, H atoms omitted for clarity. (C) Stacking of 8 with Pt(ii)⋯Pt(ii) distances of 5.981 Å and 7.979 Å
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We report the synthesis and characterization of a series of d⁸ metal complexes featuring robust and photophysically innocent strong-field chelating 1,1′-bis(o-carborane) (bc) ligand frameworks. A combination of UV-Vis spectroscopy, single crystal X-ray structural analysis, and DFT calculations of these species suggest that the dianionic bc ligand d...
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Citations
... This (bio)isosteric replacement strategy has been widely applied in medicinal chemistry (as well as in catalysis and materials science) and often yielded increased selectivity and potency, as well as decreased toxicity. [37][38][39][40][41][42][43][44][45][46] Carboranes represent a group of polyhedral clusters composed of CH and BH vertices, with the icosahedral closodicarbadodecaborane (C 2 B 10 H 12 ) standing out as the most prominent and extensively studied member. [37,39,45,47,48] The two carbon atoms within the icosahedron (prefix/cluster positions of carbon) can be positioned creating a separation by one (ortho/ 1,2), two (meta/1,7), or three (para/1,12) bonds corresponding to three isomers. ...
... [37][38][39][40][41][42][43][44][45][46] Carboranes represent a group of polyhedral clusters composed of CH and BH vertices, with the icosahedral closodicarbadodecaborane (C 2 B 10 H 12 ) standing out as the most prominent and extensively studied member. [37,39,45,47,48] The two carbon atoms within the icosahedron (prefix/cluster positions of carbon) can be positioned creating a separation by one (ortho/ 1,2), two (meta/1,7), or three (para/1,12) bonds corresponding to three isomers. The cluster fragments CH and BH are linked together through a robust network of multi-electron-multicentre bonds, forming a fully delocalised three-dimensional σaromatic compound, often referred to as a "superaromatic" structure due to its exceptional stability. ...
This study proposes an innovative strategy to enhance the pharmacophore model of antimicrobial bismuth thiolato complex drugs by substituting hydrocarbon ligand structures with boron clusters, particularly icosahedral closo‐dicarbadodecaborane (C2B10H12, carboranes). The hetero‐ and homoleptic mercaptocarborane complexes BiPh2L (1) and BiL3 (2) (L=9‐S‐1,2‐C2B10H11) were prepared from 9‐mercaptocarborane (HL) and triphenylbismuth. Comprehensive characterization using NMR, IR, MS, and XRD techniques confirmed their successful synthesis. Evaluation of antimicrobial activity in a liquid broth microdilution assay demonstrated micromolar to submicromolar minimum inhibitory concentrations (MIC) suggesting high effectiveness against S. aureus and limited efficacy against E. coli. This study highlights the potential of boron‐containing bismuth complexes as promising antimicrobial agents, especially targeting Gram‐positive bacteria, thus contributing to the advancement of novel therapeutic approaches.
... These species often demonstrate intriguing properties apart from their peculiar three-dimensional geometries and typical multicenter bonding interactions [13][14][15]. Some of them have been utilized in supramolecular design, ceramics, medicines, catalysis, nanomaterials, and polymer chemistry, for instance [16][17][18][19][20][21][22][23][24][25][26][27]. In parallel to the polyhedral clusters, another class of TM boron complexes with low boron content is of interest [2,8]. ...
The synthesis and structural characterization of a series of heterotrimetallic ruthenaborane clusters are reported. The photolytic reaction of nido-[(Cp*Ru)2(µ-H)2B3H7] (nido-1) (Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl) with [M(CO)5·THF] (THF = tetrahydrofuran, M = Mo and W) yielded the heterotrimetallic clusters pileo-[(Cp*Ru)2{M(CO)3}(µ-CO)(µ-H)(µ3-BH)B2H5], M = Mo (2), W (3) and the known arachno ruthenaboranes [1,2-(Cp*Ru)(Cp*RuCO)(µ-H)B3H8] (I) and [{Cp*Ru(CO)}2B2H6] (II). In an attempt to synthesize the Mn-analog of 2 and 3, we performed a similar reaction of nido-1 with [Mn2(CO)10], which afforded the heterotrimetallic pileo-[(Cp*Ru){Mn(CO)3}(µ-H)2(µ3-BH)B2H5] (4) cluster along with the reported trimetallic hydrido(hydroborylene) species [(Cp*Ru)2{Mn(CO)3}(µ-H)(µ-CO)3(µ-BH)] (III). Ruthenaboranes 2, 3 and 4 are isoelectronic and isostructural. The geometry of 2–4 can be viewed as a triangle face-fused square pyramidal and tetrahedral geometry, in which the apical vertex of the tetrahedron is occupied by a µ3–BH moiety. All of these pileo ruthenaborane clusters obey Mingos’ fusion formalism. Clusters 2–4 were characterized using multinuclear NMR, IR spectroscopies and electrospray ionization mass spectrometry. The single-crystal X-ray diffraction studies of clusters 2 and 4 confirmed their structures. Further, density functional theory (DFT) studies of these pileo ruthenaboranes have been carried out to investigate the nature of bonding, fusion and electronic structures.
... Higher polyhedral boranes [B n H n ] 2− (n = 10, 12) are the subjects of numerous studies. Traditionally, boron cluster anions are used as agents for boron neutron capture therapy (BNCT) [1][2][3][4][5], high-energy materials, non-coordinating anions, and ligands [6][7][8][9][10][11][12]. In recent years, this class of compounds has been utilized as optical [13][14][15][16][17] and magnetic [18][19][20][21] materials, chemical reaction catalysts [22][23][24][25], and materials for photovoltaics [26][27][28]. ...
... The closo-dodecaborate dianion [B 12 H 12 ] 2− is a spatially aromatic system with delocalized electrons, which accounts for the high thermal and kinetic stability of its derivatives and their tendency to undergo substitution reactions of the exo-polyhedral hydrogen atom [29]. Due to the high symmetry of the closo-dodecaborate anion [B 12 H 12 ] 2− (symmetry group I h ), the anion lacks a distinct reaction center. ...
... The closo-dodecaborate dianion [B 12 H 12 ] 2− is a spatially aromatic system with delocalized electrons, which accounts for the high thermal and kinetic stability of its derivatives and their tendency to undergo substitution reactions of the exo-polyhedral hydrogen atom [29]. Due to the high symmetry of the closo-dodecaborate anion [B 12 H 12 ] 2− (symmetry group I h ), the anion lacks a distinct reaction center. Consequently, obtaining monosubstituted derivatives of the closo-dodecaborate anion is often complicated by the formation of poly-substituted products. ...
By reacting nitrilium derivative of the closo-dodecaborate anion, Bu4N[B12H11N≡CR] (where R = Me, Et, nPr, iPr, p-tolyl), with lithium aluminum hydride (LiAlH4), N-alkylammonium derivatives of the closo-dodecaborate anion, and Bu4N[B12H11NH2CH2R], were obtained. The reduction reaction procedure was optimized, achieving yields close to quantitative (90–95%). The structure of the compound Bu4N[B12H11NH2CH2CH3] was determined using X-ray structural analysis. It was found that substituting lithium aluminum hydride (LiAlH4) with sodium borohydride (NaBH4) leads to the same products but only upon heating, while the reaction with LiAlH4 proceeds at room temperature.
... Luminescent metal complexes (LMC's) have received enormous attention because of their outlandish photophysical and enriched redox behaviors. [1][2][3][4][5][6][7][8] Among them, researchers concentrated on the platinum group metals having d6 system such as Ir(III), and Pt(IV), thanks to excellent phosphorescence properties and stoke shifts. [9,10] Pt(IV) complexes with cyclometallated 2-(9,9-dimethylfluoren-2-yl)pyridine (flpy), [11] deprotonated 2-phenylpyridine with different functional ligands [12] and N,N-diphenyl-6-(1H-pyrazol-1-yl)pyridin-2amine [2] have exhibited phosphorescence with a good emission efficiency, long lifetime and high absorptivity. ...
The synthesis, characterization, electro and photophysical properties of eight cyclometallated platinum (IV) complexes 6a–6d and 7a–7d derived from quinoline Schiff base ligands are reported. Spectral studies revealed that nonparticipation of nitrogen atom and participation of carbon atom of the quinoline ring in the bond formation through [NN′C] mode of coordination for complex 6, whereas [N S O] mode of coordination with octahedral geometry for complex 7. The absorption and emission spectra studied in acetonitrile medium at room temperature showed that the ligand charge transitions within the quinoline Schiff base ligands with Metal Ligand Charge Transfer (MLCT) character. The broad band appeared in the range of 460–502 nm is attributed to the higher emission intensities of cyclometallated platinum (IV) compounds. The HOMO, LUMO and energy gap of the synthesized complexes was found to be − 2.60 eV, −4.75 eV and 2.15 eV through Density Functional Theory (DFT).
... [12][13][14][15][16][17][18][19][20][21][22][23][24] The strong electron withdrawing property of o-carborane, which originates from the high polarizability of its σaromaticity [25][26][27][28] via the high Lewis acidity of the ten boron atoms in a cluster, is predominantly responsible for its intriguing photophysical properties when the carbon atom in the cluster is substituted with conjugated π-aromatic moieties. [29][30][31][32][33] Such features enable intramolecular charge-transfer (ICT) transitions in the conjugated system, resulting in the formation of electronic donor (D, π-aromatic group)-acceptor (A, o-carborane) dyad complexes. The o-carboranyl D-A dyad system can exhibit unique ICT-based emission. ...
Naphthyl‐ and quinoline‐appended o‐carboranyl compounds, NCB and QCB, respectively, were prepared and characterized by multinuclear nuclear magnetic resonance spectroscopy, elemental analysis, and single crystal X‐ray diffraction. Although both the compounds were non‐emissive in the solution state at 298 K, they were photoluminescent in the rigid state (in THF at 77 K and film state) in the region 450–550 nm. Theoretical calculation of the optimized structure in the S1 state suggested that the low‐energy emissive bands for NCB and QCB were attributed to intramolecular charge transfer (ICT) transition. Intriguingly, the C−C bond axis of the o‐carborane in NCB in the solid state was more orthogonal to the plane of the appended aromatic group than that in QCB, indicating relatively high delocalization between the o‐carborane and aromatic moieties of NCB. The quantum efficiency and radiative decay constant of the ICT‐based emission of NCB in the film state were much higher than those of QCB. These findings imply that the structural geometry around the C−C bond axis of the o‐carborane is a decisive factor in accelerating the ICT‐based radiative decay in the o‐carbonyl luminophores in the rigid state.
... All of the prepared closo-and nido-o-carboranyl compounds were fully characterized using multinuclear ( 1 H{ 11 B}, 13 C, and 11 B{ 1 H}) NMR spectroscopy (Figures S1-S12 in the Supplementary Material) and elemental analysis. The 1 H and 13 C NMR spectra of closo-DT and closo-PT exhibited resonances corresponding to the terphenyl moieties. ...
... All nuclear magnetic resonance (NMR) spectra were recorded on a Bruker Avance 400 spectrometer (400.13 MHz for 1 H, 100.62 MHz for 13 ...
Closo-o-carboranyl compounds bearing the ortho-type perfectly distorted or planar terphenyl rings (closo-DT and closo-PT, respectively) and their nido-derivatives (nido-DT and nido-PT, respectively) were synthesized and fully characterized using multinuclear NMR spectroscopy and elemental analysis. Although the emission spectra of both closo-compounds exhibited intriguing emission patterns in solution at 298 and 77 K, in the film state, closo-DT mainly exhibited a π-π* local excitation (LE)-based emission in the high-energy region, whereas closo-PT produced an intense emission in the low-energy region corresponding to an intramolecular charge transfer (ICT) transition. In particular, the positive solvatochromic effect of closo-PT and theoretical calculation results at the first excited (S1) optimized structure of both closo-compounds strongly suggest that these dual-emissive bands at the high- and low-energy can be assigned to each π-π* LE and ICT transition. Interestingly, both the nido-compounds, nido-DT and nido-PT, exhibited the only LE-based emission in solution at 298 K due to the anionic character of the nido-o-carborane cages, which cannot cause the ICT transitions. The specific emissive features of nido-compounds indicate that the emissive color of closo-PT in solution at 298 K is completely different from that of nido-PT. As a result, the deboronation of closo-PT upon exposure to increasing concentrations of fluoride anion exhibits a dramatic ratiometric color change from orange to deep blue via turn-off of the ICT-based emission. Consequently, the color change response of the luminescence by the alternation of the intrinsic electronic transitions via deboronation as well as the structural feature of terphenyl rings indicates the potential of the developed closo-o-carboranyl compounds that exhibit the intense ICT-based emission, as naked-eye-detectable chemodosimeters for fluoride ion sensing.
... Icosahedral carboranes are a class of carbon-boron molecular clusters with three dimensional aromaticity analogues to benzene, the features of high boron content, extraordinary thermal and chemical stability, and synthetic flexibility make the carborane derivatives be a kind of important building blocks in functional materials [1][2][3][4], key frameworks in pharmaceuticals [5][6][7][8] and ligands in organometallic chemistry [9][10][11][12][13]. Therefore, the selective functionalization of carboranes has attracted considerable interest from chemists [14][15][16][17][18]. ...
Aromatic heterocycles are ubiquitous building blocks in bioactive natural products, pharmaceutical and agrochemical industries. Accordingly, the carborane-fused heterocycles would be potential candidates in drug discovery, nanomaterials, metallacarboranes, as well as photoluminescent materials. In recent years, the transition metal catalyzed B-H activation has been proved to be an effective protocol for selective functionalization of B-H bond of o-carboranes, which has been further extended for the synthesis of polyhedral borane cluster-fused heterocycles via cascade B-H functionalization/annulation process. This article summarizes the recent progress in construction of polyhedral borane cluster-fused heterocycles via B-H activation.
... E2 was prepared as a white solid (0.65 g; yield = 95.5%) in a procedure analogous to that used for E1, with S2 (0.83 g, 2.0 mmol) and K 2 CO 3 (0.55 g, 4.0 mmol). 1 13 ...
... H NMR (CDCl 3 ): δ 8.30 (d, J = 8.4 Hz, 1H), 7.83 (d, J = 7.6 Hz, 2H), 7.70 (m, 1H), 7.37 (m, 3H), 7.03 (m, 3H), 7.05 (m, 1H), 6.74 (dd, J = 7.6, 1.1 Hz, 1H), 6.69 (dd, J = 7.4, 1.0 Hz, 1H), 6.64 (d, J = 7.6 Hz, 2H), 5.02 (s, 1H, CB-H), 2.56-1.36 (br, 10H, CB-BH).13 C NMR (CDCl 3 ): δ 152.32, 149.84, 148.41, 141.91, 139.51, 137.76, 131.53, 130.32, 128.80, 128.25, 128.23, 127.87, 127.79, 125.83, 125.26, 125.08, 123.97, 120.36, 77.76 (CB-C), 65.78 (spiro-C) 59.85 (CB-C). ...
9,9′-Spirobifluorene-based o-carboranyl compounds C1 and C2 were prepared and fully characterized by multinuclear nuclear magnetic resonance (NMR) spectroscopy and elemental analysis. The solid-state structure of C1 was also determined by single-crystal X-ray diffractometry. The two carboranyl compounds display major absorption bands that are assigned to π−π* transitions involving their spirobifluorene groups, as well as weak intramolecular charge-transfer (ICT) transitions between the o-carboranes and their spirobifluorene groups. While C1 only exhibited high-energy emissions (λem = ca. 350 nm) in THF at 298 K due to locally excited (LE) states assignable to π−π* transitions involving the spirobifluorene group alone, a remarkable emission in the low-energy region was observed in the rigid state, such as in THF at 77 K or the film state. Furthermore, C2 displays intense dual emissive patterns in both high- and low-energy regions in all states. Electronic transitions that were calculated by time-dependent-DFT (TD-DFT) for each compound based on ground (S0) and first-excited (S1) state optimized structures clearly verify that the low-energy emissions are due to ICT-based radiative decays. Calculated energy barriers that are based on the relative energies associated with changes in the dihedral angle around the o-carborane cages in C1 and C2 clearly reveal that the o-carborane cage in C1 rotates more freely than that in C2. All of the molecular features indicate that ICT-based radiative decay is only available to the rigid state in the absence of structural fluctuations, in particular the free-rotation of the o-carborane cage.
... 12 In turn, the treatment of these species with small molecules (CO, MeCN) cleaved the Bagostic B−H⇀Ru bond and afforded the first examples of closo-closo-X 2 (C,B′) coordination of bis(carborane), 12 a bonding mode subsequently reported by others. 17 Compound I was found to be an efficient Lewis acid catalyst for Diels−Alder cycloaddition, presumably operating through initial displacement of the B-agostic B−H⇀Ru interaction by the substrate. In this contribution, we describe the results of experiments designed to tune the Lewis acidity of the metal center by varying the η-arene ligand. ...
... Partial deboronation of 1,1′-bis(ortho-carborane) in the presence of n BuLi in THF has been noted previously. 17,24 We believe that the most likely source of this deboronation is nucleophilic attack on 1,1′-bis(ortho-carborane) by an ω-alkenolate ion formed by the decomposition of THF by n BuLi at room temperature. 40 We therefore concur with Spokoyny et al. that n BuLi is not a suitable reagent for the deprotonation of 1,1′bis(ortho-carborane). ...
Deprotonation of 1,1'-bis(ortho-carborane) with
n
BuLi in THF followed by reaction with [RuCl2(p-cymene)]2 affords, in addition to the known compound [Ru(κ3-2,2',3'-{1-(1'-closo-1',2'-C2B10H10)-closo-1,2-C2B10H10)}(p-cymene)] (I), a small amount of a new species, [Ru(κ3-2,2',11'-{1-(7'-nido-7',8'-C2B9H11)-closo-1,2-C2B10H10)}(p-cymene)] (1a), with two B-agostic B-H⇀Ru bonds, making the bis(carborane) unit a closo-nido-X(C)L2 ligand, a previously unreported bonding mode. Similar species were also formed with arene = benzene (1b), mesitylene (1c), and hexamethylbenzene (1d), although in the last two cases the metallacarborane-carborane species [1-(1'-closo-1',2'-C2B10H11)-3-(arene)-closo-3,1,2-RuC2B9H10)], 2c and 2d, were also isolated. With the bis(ortho-carborane) transfer reagent [Mg(κ2-2,2'-{1-(1'-closo-1',2'-C2B10H10)-closo-1,2-C2B10H10)}(DME)2], the target compounds [Ru(κ3-2,2',3'-{1-(1'-closo-1',2'-C2B10H10)-closo-1,2-C2B10H10)}(arene)], 4b and 4d, were prepared in reasonable-to-good yields, although for arene = benzene and mesitylene small amounts of the unique paramagnetic species [{Ru(arene)}2(μ-Cl)(μ-κ4-2,2',3,3'-{1-(1'-closo-1',2'-C2B10H9)-closo-1,2-C2B10H9})], 3b and 3c, were also formed. In compounds 3, the bis(carborane) acts as a closo-closo-X4(C,C',B,B') ligand to the Ru2 unit. In I, 4b, and 4d, the B-agostic B-H⇀Ru bond is readily cleaved by MeCN, affording compounds [Ru(κ2-2,2'-{1-(1'-closo-1',2'-C2B10H10)-closo-1,2-C2B10H10})(arene)(NCMe)] (5a, 5b, and 5d) and suggesting that I, 4b, and 4d could act as Lewis acid catalysts, which is subsequently shown to be the case for the Diels-Alder cycloaddition reactions between cyclopentadiene and methacrolein, ethylacrolein and E-crotonaldehyde. All new species were characterized by multinuclear NMR spectroscopy and 1a, 1c, 1d, 2c, 2d, 3b, 3c, 4b, 4d, 5a, 5b, and 5d were also characterized crystallographically.
... Therefore, they do not appear as numerously in the literature as emitter materials for OLEDs. Some recent articles have evidenced the increasing interest for emitting Ni(II) complexes [297][298][299][300][301], although none of the reference papers reported the electroluminescent properties, while the biggest attention reserved to nickel(II) complexes is reserved for their application in catalysis [302,303]. ...
Organic light-emitting diodes (OLEDs) produced from metal complexes play an important role in modern electroluminescent devices. While OLEDs are being used in display various applications such as TVs, smartphones and wearables already, a drastic increase in the production volume in the next years is being expected as soon as OLED lighting applications and printed OLEDs hit the market. Given that thus far, phosphorescent iridium compounds are required to make these products, sustainability issues are imminent. To review viable alternatives, we highlight the current status of sustainable metal complexes with a special focus on copper and zinc complexes. Ligand structures and complex preparation were highlighted. We also briefly address features like cooperativity, chirality, and printing.
