Azanonaboranes containing imidazole derivatives for boron neutron capture therapy: synthesis, characterization, and in vitro toxicity evaluation

A number of azanonaboranes containing imidazole derivatives have been synthesized by a ligand-exchange reaction. The exo-NH(2)R group of the azanonaborane of the type [(RH(2)N)B(8)H(11)NHR] can be exchanged by one hetero-nitrogen atom of the imidazole ring. In the case of histamine, the exchange takes place on the aliphatic amino group, the hetero-nitrogen atom of the imidazole ring or both of them. The products were confirmed by NMR, IR spectroscopy, elemental analysis, and mass spectrometry. The electron-withdrawing effect of the nitro group in 2-nitroimidazole is the main hindrance to achieve the exchange reaction. In vitro experiments were performed with B16 melanoma cells. A comparison of the biological properties of the products in which the B(8)N cluster is connected to the hetero-nitrogen atom of imidazole ring or the aliphatic NH(2) group showed that incorporation of B(8)N cluster unit into primary amino group increases the compound's toxicity. In contrast, this specificity for cytotoxicity effect was not observed in the case of histamine containing two B(8)N clusters which was relatively nontoxic and did not inhibit colony formation up to concentrations of 2 mM.     

A family of ferro- and antiferromagnetically coupled decametallic chromium(III) wheels

The synthesis and crystal structures of a family of decametallic Cr(III) "molecular wheels" are reported, namely [Cr10(OR)20(O2CR')10] [R' = Me, R = Me (1), Et (2); R' = Et, R = Me (3), Et (4); R' = CMe3, R = Me (5), Et (6)]. Magnetic studies on 1-6 reveal a remarkable dependence of the magnetic behaviour on the nature of R. In each pair of complexes with a common carboxylate (R') the nearest neighbour CrCr magnetic exchange coupling is more antiferromagnetic for the ethoxide-bridged (R = Et) cluster than for the methoxide analogue. In complexes 2, 4 and 6 the overall coupling is weakly antiferromagnetic resulting in diamagnetic (S = 0) ground states for the cluster, whilst in 1 and 5 it is weakly ferromagnetic thus resulting in very high-spin ground states. This ground state has been probed directly in the perdeuterated version of 1 ([D]1) by inelastic neutron scattering experiments, and these support the S = 15 ground state expected for ferromagnetic coupling of ten Cr(III) ions, and they also indicate that a single J-value model is inadequate. The ground state of 5 is large but not well defined. The trends in J on changing R are further supported by density functional calculations on 1-6, which are in excellent agreement with experiment. The very large changes in the nature of the ground state between 1 and 2, and 5 and 6 are the result of relatively small changes in J that happen to cross J = 0, hence changing the sign of J.     

Diastereoselective fragmentation of chiral alpha-aminophosphonic acids/metal ion aggregates

Diastereomeric clusters of general formula [MAB(2)](+) and [MA(2)B](+) (M = Li(I), Na(I), Ag(I), Ni(II)-H, or Cu(II)-H; A = (R)-(-)- and (S)-(+)-(1-aminopropyl)phosphonic acid; B = (1R)-(-)- and (1S)-(+)-(1-aminohexyl)phosphonic acid) have been readily generated in the electrospray ionization (ESI) source of a triple-quadrupole mass spectrometer and their collision-induced dissociation (CID) investigated. CID of diastereomeric complexes, e.g. [MA(S)(B(S))(2)](+) and [MA(R)(B(S))(2)](+), leads to fragmentation patterns characterized by R(homo) = [MA(S)B(S)](+)/[M(B(S))(2)](+) and R(hetero) = [MA(R)B(S)](+)/[M(B(S))(2)](+) abundance ratios, which depend upon the relative stability of the diastereomeric [MA(S)B(S)](+) and [MA(R)B(S)](+) complexes in the gas phase. The chiral resolution factor R(chiral) = R(homo)/R(hetero) is found to depend not only on the nature of the M ion but also on that of the fragmenting species, whether [MAB(2)](+) or [MA(2)B](+). The origin of this behavior is discussed.     

Some complexes containing Pt-C5-Co3 fragments: Molecular structure of trans-Pt{CCCC-μ3-C[Co3(μ-dppm)(CO)6(PPh3)]}2(PPh3)2 determined using synchrotron radiation

Reactions of platinum(II) chloro-phosphine complexes with Co₃(μ₃-CCCCCSiMe₃)(μ-dppm)(CO)₇ in the presence of NaOMe have given the compounds Pt{CCCC-μ₃-C[Co₃(μ-dppm)(CO)₇]}₂(dppe) (1), trans-Pt{CCCC-μ₃-C[Co₃(μ-dppm)(CO)₇]}₂(PEt₃)₂ (2) and trans-Pt{CCCC-μ₃-C[Co₃(μ-dppm) (CO)₆(PPh₃)]}₂(PPh₃)₂ (3), each of which contains two Co₃ clusters linked by C₅ chains to the Pt centre. Electrochemical studies (CVs) show the presence of both oxidation and reduction processes, the latter probably occurring on the CCo₃ cores. Ready reductive elimination of {Co₃(μ-dppm)(CO)₇}₂(μ₃:μ₃-C₁₀) occurs from 1 upon heating. The X-ray study of 3 was carried out using synchrotron radiation (Advanced Photon Source, Argonne, IL) to confirm its structure.     

Synthesis, single crystal X-ray analysis, and TEM for a single-sized Au11 cluster stabilized by SR ligands: The interface between molecules and particles

An SR-modified Au cluster with a sub-nanometer size, Au₁₁(S-4-NC₅H₄)₃(PPh₃)₇ (1), has been synthesized by NaBH₄ reduction of Au(S-py)(PPh₃) or by reacting [Au₉(PPh₃)₈](NO₃)₃ with HS-4-py in good yield. Its molecular structure has been elucidated by single crystal X-ray diffraction, and TEM observation has been achieved for the first time for this size of SR-modified Au clusters. The core structure is best described in terms of an incomplete icosahedron. CV measurements in CH₂Cl₂ have suggested that the cluster does not coagulate in solution with significant concentration.     

Alkynyl and poly-ynyl derivatives of carbon-tricobalt clusters

A series of alkynyl-tricobalt carbonyl clusters, Co₃(μ₃-C_nR)(μ-dppm)(CO)₇ [R = Bu^t, Ph, C₆H₄I, C₆H₄CCPh, SiMe₃, Fc, Au(PPh₃)] containing three, five or seven carbons in the chain, have been prepared by elimination of phosphine-gold(I) halides in reactions between Co₃(μ₃-CBr)(μ-dppm)(CO)₇ and Au(CCR)(PPh₃) or between Co₃{μ₃-CCCAu(PR₃)} (μ-dppm)(CO)₇ (R = Ph, tol) and ICCR′ (R′ = SiMe₃, Fc). The use of poly-substituted arenes or ferrocenes has enabled preparation of the complexes 1,4-{(OC)₇(μ-dppm)Co₃ (μ₃-CCC)}₂C₆H₃X-5 (X = H, Br), 1,3,5-{(OC)₇(μ-dppm)Co₃(μ₃-CCC)}₃C₆H₃ and 1,1′-{(OC)₇(μ-dppm)Co₃ (μ₃-CCC)}₂Fc′ [Fc′ = Fe(η-C₅H₄-)₂]. The X-ray determined molecular structures of 12 of the complexes are reported.     

Synthesis and structure of cluster compounds containing a novel cluster core {Re4STe3}

Three novel cluster compounds K₄[Re₄STe₃(CN)₁₂]·₄H₂O (I), [{Cu(en)₂}₂Re₄STe₃(CN)₁₂]·₅H₂O (II) and [{Cu(trien)}₂Re₄STe₃(CN)₁₂]·2H₂O (III) (en is ethylenediamine, trien is triethylenetetraamine) containing a new cluster core {Re₄STe₃} have been prepared and structurally characterized. According to single crystal X-ray diffraction data, compound I is ionic and represents the arrangement of ions K⁺ and [Re₄STe₃(CN)₁₂]^4?; compounds II and III are molecular and formed by two cationic moieties {Cu(en)₂}²⁺ and {Cu(trien)}²⁺, respectively, coordinated to one cluster anion. In the solid state, S atom positions in the tetrahedron Q₄ (Q = S, Te) are disordered for all three compounds: in I and III sulfur atoms are split over all four Q positions, while in II over two positions.     

测地极坐标下空间形式的度量特征

将R3中Gauss曲率为常数k0的常曲率曲面S的度量特征推广到了一般的空间形式,主要工作是利用活动标架法和测地极坐标的理论,通过对结构方程的微分,找到了关于度量的一个内在方程,由此给出了定理的一个证明。     

Quantum Information Splitting of an Arbitrary Three-Qubit State by Using Cluster States and Bell States

A new application of cluster states is investigated for quantum information splitting (QIS) of an arbitrary three-qubit state. In our scheme, a four-qubit cluster state and a Bell state are shared by a sender (Alice), a controller (Charlie), and areceiver (Bob). Both the sender and controller only need to perform Bell-state measurements (BSMs), the receiver can reconstruct the arbitrary three-qubit state by performing some appropriately unitary transformations on his qubits after he knows the measured results of both the sender and the controller. This QIS scheme is deterministic.     

On quantum cluster algebras of finite type

We extend the definition of a quantum analogue of the Caldero-Chapoton map defined by D. Rupel. When Q is a quiver of finite type, we prove that the algebra (Q) generated by all cluster characters is exactly the quantum cluster algebra (Q).