气相中烯丙基负离子与N2O反应机理

采用二阶微扰理论的MP2/6-31G(d,p)方法对气相中烯丙基负离子与N2O的反应机理进行了理论计算研究, 并在相同基组下进一步用CCSD(T)方法进行了单点能的校正. 计算结果表明, 该反应存在三条反应通道, 产物分别为cis-CH2CHCNN-+H2O, trans-CH2CHCNN-+H2O和CH2CCH-+N2+H2O, 其中生成cis-CH2CHCNN-和trans-CH2CHCNN-的两条通道为相互竞争的主反应通道, 计算结果与实验相吻合. 同时利用传统的过渡态理论, 计算了各反应通道在298 K时, 速控步骤的反应速率常数k(T).     

Effect of the H-bonding on aromaticity of purine tautomers

Four tautomers of purine (1-H, 3-H, 7-H, and 9-H) and their equilibrium H-bonded complexes with F(-) and HF for acidic and basic centers, respectively, were optimized by means of the B3LYP/6-311++G(d,p) level of theory. Purine tautomer stability increases in the following series: 1-H < 3-H < 7-H < 9-H, consistent with increasing aromaticity. Furthermore, the presence of a hydrogen bond with HF does not change this order. For neutral H-bonded complexes, the strongest and the weakest intermolecular interactions occur (-14.12 and -10.49 kcal/mol) for less stable purine tautomers when the proton acceptor is located in the five- and six-membered rings, respectively. For 9-H and 7-H tautomers the order is reversed. The H-bond energy for the imidazole complex with HF amounts to -14.03 kcal/mol; hence, in the latter case, the fusion of imidazole to pyrimidine decreases its basicity. The ionic H-bonds of N(-)···HF type are stronger by ~10 kcal/mol than the neutral N···HF intermolecular interactions. The hydrogen bond N(-)···HF energies in pyrrole and imidazole are -32.28 and -30.03 kcal/mol, respectively, and are substantially stronger than those observed in purine complexes. The aromaticity of each individual ring and of the whole molecule for all tautomers in ionic complexes is very similar to that observed for the anion of purine. This is not the case for neutral complexes and purine as a reference. The N···HF bonds perturb much more the π-electron structure of five-membered rings than that of the six-membered ones. The H-bonding complexes for 7-H and 9-H tautomers are characterized by higher aromaticity and a much lower range of HOMA variability.     

Theoretical study for pyridinium-based ionic liquid 1-ethylpyridinium trifluoroacetate: synthesis mechanism, electronic structure, and catalytic reactivity

By performing density functional theory calculations, we have studied the synthesis mechanism, electronic structure, and catalytic reactivity of a pyridinium-based ionic liquid, 1-ethylpyridinium trifluoroacetate ([epy](+)[CF(3)COO](-)). It is found that the synthesis of the pyridinium salt follows a S(N)2 mechanism. The electronic structural analyses show that multiple H bonds are generally involved in the pyridinium-based ionic liquid, which may play a decisive role for stabilizing the ionic liquid. The cation-anion interaction mainly involves electron transfer between the lone pair of the oxygen atom in the anion and the antibonding orbital of the C*-H bond (C* denotes the carbon atom at the ortho-position of nitrogen atom in the cation). This present work has also given clearly the catalytic mechanism of [epy](+)[CF(3)COO](-) toward to the Diels-Alder (D-A) reaction of acrylonitrile with 2-methyl-1,3-butadiene. Both the cation and anion are shown to play important roles in promoting the D-A reaction. The cation [epy](+), as a Lewis acid, associates the C≡N group by C≡N···H H bond to increase the polarity of the C═C double bond in acrylonitrile, while the anion CF(3)COO(-) links with the methyl group in 2-methyl-1,3-butadiene by C-H···O H bond, which weakens the electron-donating capability of methyl and thereby lowers the energy barrier of the D-A reaction. The present results are expected to provide valuable information for the design and application of pyridinium-based ionic liquids.     

Unexpected metal-induced isomerisms and phosphoryl migrations in Pt(II) and Pd(II) complexes of the functional phosphine 2-(bis(diphenylphosphino)methyl)-oxazoline

The reaction of the functional diphosphine 1 [1 = 2-(bis(diphenylphosphino)methyl-oxazoline] with [PtCl(2)(NCPh)(2)] or [PdCl(2)(NCPh)(2)], in the presence of excess NEt(3), affords [Pt{(Ph(2)P)(2)C···C(···NCH(2)CH(2)O)}(2)] ([Pt(1(-H)-P,P)(2)], 3a) and [Pd{(Ph(2)P)(2)C···C(···NCH(2)CH(2)O)}(2)] ([Pd(1(-H)-P,P)(2)], 3b), respectively, in which 1(-H) is (oxazoline-2-yl)bis(diphenylphosphino)methanide. The reaction of 3b with 2 equiv of [AuCl(tht)] (tht = tetrahydrothiophene) afforded [Pd(1(-H)-P,N)(2)(AuCl)(2)] (4), as a result of the opening of the four-membered metal chelate since ligand 1(-H), which was P,P-chelating in 3b, behaves as a P,N-chelate toward the Pd(II) center in 4 and coordinates to Au(I) through the other P donor. In the absence of a base, the reaction of ligand 1 with [PtCl(2)(NCPh)(2)] in MeCN or CH(2)Cl(2) afforded the isomers [Pt{(Ph(2)P)(2)C═C(OCH(2)CH(2)NH)}(2)]Cl(2) ([Pt(1'-P,P)(2)]Cl(2) (5), 1' = 2-(bis(diphenylphosphino)methylene)-oxazolidine) and [Pt{(Ph(2)P)(2)C═C(OCH(2)CH(2)NH)}{Ph(2)PCH═C(OCH(2)CH(2)N(PPh(2))}]Cl(2) ([Pt(1'-P,P)(2'-P,P)]Cl(2) (6), 2' = (E)-3-(diphenylphosphino)-2-((diphenylphosphino)methylene)oxazolidine]. The P,P-chelating ligands in 5 result from a tautomeric shift of the C-H proton of 1 to the nitrogen atom, whereas the formation of one of the P,P-chelates in 6 involves a carbon to nitrogen phosphoryl migration. The reaction of 5 and 6 with a base occurred by deprotonation at the nitrogen to afford 3a and [Pt{(Ph(2)P)(2)C···C(···NCH(2)CH(2)O)}{Ph(2)PCH═COCH(2)CH(2)N(PPh(2))}]Cl ([Pt(1(-H)-P,P)(2'-P,P)]Cl (7)], respectively. In CH(2)Cl(2), an isomer of 3a, [Pt{Ph(2)P)(2)C···C(···NCH(2)CH(2)O)}{Ph(2)PC(PPh(2))═COCH(2)CH(2)N}] ([Pt(1(-H)-P,P)(1(-H)-P,N)] (8)), was obtained as a side product which contains ligand 1(-H) in two different coordination modes. Complexes 3b·4CH(2)Cl(2), 4·CHCl(3), 6·2.5CH(2)Cl(2), and 8·CH(2)Cl(2) have been structurally characterized by X-ray diffraction.     

Template-directed synthesis of kinetically and thermodynamically stable molecular necklace using ring closing metathesis

We report the template-directed synthesis of a well-defined, kinetically stable [5]molecular necklace with dialkylammonium ion (R(2)NH(2)(+)) as recognition site and DB24C8 as macrocycle. A thread containing four dialkylammonium ions with olefin at both ends was first synthesized and then subjected to threading with an excess amount of DB24C8 to form pseudo[5]rotaxane, which in situ undergoes ring closing metathesis at the termini with second generation Grubbs catalyst to yield the desired [5]molecular necklace. The successful synthesis of [5]molecular necklace is mainly attributed to the self-assembly and dynamic covalent chemistry which allows the formation of thermodynamically most stable product. The self-assembly of the DB24C8 ring onto the recognition site known as templating effect was driven by noncovalent stabilizing interactions like [N(+)-H···O], [C-H···O] hydrogen bonds as well as [π···π] interactions which is facilitated in non-polar solvents. The reversible nature of olefin metathesis reaction makes it suitable for dynamic covalent chemistry since proof-reading and error-checking operates until it generates thermodynamically the most stable interlocked molecule. Riding on the success of [5]molecular necklace, we went a step further and attempted to synthesize [7]molecular necklace using the same protocol. This led to the synthesis of another thread with olefin at both ends but having six dibenzylammonium ions along the thread. However, the extremely poor solubility of this thread containing six secondary ammonium ions limits the self-assembly process even after we replaced the typical PF(6)(-) counter anion with a more lipophilic BPh(4)(-) anion. Although the poor solubility of the thread remains the bottleneck for making higher order molecular necklaces yet this approach of "threading-followed-by-ring-closing-metathesis" for the first time produces kinetically and thermodynamically stable, well-defined, homogeneous molecular necklace which was well characterized by one-dimensional, two-dimensional, variable temperature proton NMR spectroscopy and ESI mass spectroscopy.     

Conformational analysis of 1-butyl-3-methylimidazolium by CCSD(T) level ab initio calculations: effects of neighboring anions

Conformational energies for the butyl group of 1-butyl-3-methylimidazolium (bmim) were calculated by high-level ab initio methods. Estimated relative energies for the TT, GT and G'T rotamers of an isolated bmim cation at the CCSD(T)/cc-pVTZ level are 0.0 -0.02 and -0.50 kcal/mol, respectively. The close contact of a Cl anion to theC(2)-H of imidazolium considerably increases the relative stability of the GT rotamer. Estimated relative energies for the three rotamers of the [bmim]Cl complex, in which the Cl anion exists close to the C(2)-H, are 0.0, -1.61 and -0.25 kcal/mol, respectively. The GT rotamer is favored by the strong attractive electrostatic interaction between the bmim cation and Cl anion. The C(2)-H group in the GT rotamer has a larger positive charge compared with those in the TT and G'T rotamers. The contact of a Br anion to the C(2)-H also stabilizes the GT rotamer. The effects of the Cl anion close to the C(4)-Hand C(5)-Hare small. The anion effects suggest that the GT rotamer is the most stable in ionic liquids. The positive charge on imidazolium ring does not largely change the conformational energies. Estimated relative energies for the three rotamers of N-butylimidazole (0.0, -0.29 and -0.75 kcal/mol, respectively) are not largely different from those for isolated bmim. Calculated MP2/cc-pVTZ level torsional potential for the C im-N im-C-C bond has a minimum when the torsional angle is close to 90 degrees. Coplanar conformation is not a stable structure. Calculated torsional barrier height between the two nonplanar minima is less than 1 kcal/mol.     

On the weak O-H···halogen hydrogen bond: a rotational study of CH3CHClF···H2O

We measured the molecular beam Fourier transform microwave spectra of six isotopologues of the 1?:?1 adduct of CH(3)CHClF with water. Water prefers to form an O-H···F rather than an O-H···Cl hydrogen bond. This is just the contrary of what was observed in the chlorofluoromethane-water adduct, where an O-H···Cl link was formed (W. Caminati, S. Melandri, A. Maris and P. Ottaviani, Angew. Chem., Int. Ed., 2006, 45, 2438). The water molecule is linked with an O-H···F bridge to the fluorine atom, with r(F···H(w)) = 2.14 ?, and with two C-H···O contacts to the alkyl hydrogens with r(C(1)-H(1)···O(w)) = 2.75 ? and r(C(2)-H(2)···O(w)) = 2.84 ?, respectively. Besides the rotational constants, the quadrupole coupling constants of the chlorine atom have been determined. In addition, information on the internal dynamics has been obtained.     

Effect of nucleobase sequence on the proton-transfer reaction and stability of the guanine-cytosine base pair radical anion

The formation of base pair radical anions is closely related to many fascinating research fields in biology and chemistry such as radiation damage to DNA and electron transport in DNA. However, the relevant knowledge so far mainly comes from studies on isolated base pair radical anions, and their behavior in the DNA environment is less understood. In this study, we focus on how the nucleobase sequence affects the properties of the guanine-cytosine (GC) base pair radical anion. The energetic barrier and reaction energy for the proton transfer along the N(1)(G)-H···N(3)(C) hydrogen bond and the stability of GC˙(-) (i.e., electron affinity of GC) embedded in different sequences of base-pair trimer were evaluated using density functional theory. The computational results demonstrated that the presence of neighboring base pairs has an important influence on the behavior of GC˙(-) in the gas phase. The excess electron was found to be localized on the embedded GC and the charge leakage to neighboring base pairs was very minor in all of the investigated sequences. Accordingly, the sequence behavior of the proton-transfer reaction and the stability of GC˙(-) is chiefly governed by electrostatic interactions with adjacent base pairs. However, the effect of base stacking, due to its electrostatic nature, is severely screened upon hydration, and thus, the sequence dependence of the properties of GC˙(-) in aqueous environment becomes relatively weak and less than that observed in the gas phase. The effect of geometry relaxation associated with neighboring base pairs as well as the possibility of proton transfer along the N(2)(G)-H···O(2)(C) channel have also been investigated. The implications of the present findings to the electron transport and radiation damage of DNA are discussed.     

Theoretical analysis of the hydrogen bond of imidazolium C(2)-H with anions

The intermolecular interaction energies of ion pairs of imidazolium-based ionic liquids were studied by MP2/6-311G level ab initio calculations. Although the hydrogen bond between the C(2) hydrogen atom of an imidazolium cation and anion has been regarded as an important interaction in controlling the structures and physical properties of ionic liquids as in the cases of conventional hydrogen bonds, the calculations show that the nature of the C(2)-H...X interaction is considerably different from that of conventional hydrogen bonds. The interaction energies of the imidazolium cation with neighboring anions in the four crystals of ionic liquids were calculated. The size of the interaction is determined mainly by the distance between the imidazolium ring and anion. The calculated interaction energy is nearly inversely proportional to the distance, which shows that the charge-charge interaction is the dominant interaction in the attraction. The orientation of the anion relative to the C(2)-H bond does not greatly affect the size of the interaction energy. Calculated interaction energy potentials of 1,3-dimethylimidazolium tetrafluoroborate ([dmim][BF(4)]) complexes show that the C(2)-H bond does not prefer to point toward a fluorine atom of the BF(4). This shows that the C(2)-H...X hydrogen bond is not essential for the attraction.     

Hydrothermal Synthesis and Structural Characterization of two Hybrid Keggin-based Polyoxometalates

Two new hybrid polyoxotungstates, [Co（2,2＇-bipy）3][a-H5PW11CoO40]-3H2O 1 and [Fe（2,2＇-bipy）3]2[a-HBW12O40]-2.5H2O 2 （2,2＇-bipy = 2,2＇-dipyridyl）, have been hydrothermally synthesized and characterized by IR, TGA and single-crystal X-ray structural analyses. The results of X-ray crystallography analyses exhibit that 1 consists of one a-Keggin anion [a-H5PW11CoO40]2- and one isolated [Co（2,2＇-bipy）3]2＋ complex, while 2 is constructed from one a-Keggin anion [a- HBW12O40]4- and two isolated [Fe（2,2＇-bipy）3]2＋ cations. The data for 1： orthorhombic system, space group Pbcn, a = 16.062（6）, b = 27.278（10）, c = 16.951（6）A, V = 7427（5）A3 and Z = 4; and those for 2： triclinic system, space group P1, a = 13.787（3）, b = 17.857（5）, c = 18.918（5）A, a = 88.009（12）, β = 72.768（10）, γ = 74.935（10）°, V = 4291（2）A3 and Z = 2.     

1-D Selenidoindates {[In2Se5]}∞ directed by chiral metal complex cations of 1,10-phenanthroline

Two 1-D selenidoindates {[M(phen)(3)]In(2)Se(5)·H(2)O}(n) (M = Ni, Fe) were synthesized by a solvothermal method. The 1-D {[In(2)Se(5)](2-)}(n) anion is a new type of single 1-D structure constituted by an alternately fused four-membered In(2)Se(2) ring and five-membered In(2)Se(3) ring. The chalcogenoindates were separated as mechanical racemic mixtures of single enantiomer crystals, in which the R-helix of 1-D InSe anion is directed by the related clockwise (Δ) cations of [M(phen)(3)](2+) or the L-helix of 1-D anion is directed by the related anticlockwise (Λ) cation. The π···π, C···Se, and C-H···Se oriented interactions of metal complex cations with selenidoindate anions play an important role in the formation of the chiral crystals. The embedded [M(phen)(3)](2+) cations improve the optical absorption of the 1-D semiconductor materials.     

Anion photoelectron spectra and ab initio calculations of the iodide-carbon monoxide clusters: I(-)···(CO)(n), n = 1-4

Anion photoelectron spectra are reported for the iodide-carbon monoxide clusters, with supporting ab initio calculations for the 1:1 dimer anion and neutral complexes. A C(s) minimum geometry is predicted for the anion complex, while for the neutral complex two linear van der Waals minima are predicted differing in the attachment point of the iodine, that is, I···CO and I···OC. The predicted adiabatic photodetachment energy agrees well with the experimental spectrum. The photoelectron spectra feature a vibrational progression in the CO stretching mode, which becomes more pronounced for the larger clusters.     

Direct evidence for CH···π interaction mediated stabilization of Pro-cisPro bond in peptides with Pro-Pro-aromatic motifs

Although weak interactions play subtle but important roles in dictating protein structures, their experimental detection is nontrivial. From NOE experiments we provide direct evidence for the presence of CH···π interaction, operational between the C(α)-H of the first Pro and the aromatic (Aro) side chain of Xaa, in a peptide series with the general sequence Ac-Pro-Pro-Xaa-NH(2). Indirect evidence of CH···π interaction is provided from ring current-induced upfield displacement of Pro(1) C(α)-H chemical shifts and restriction of side-chain (χ1) rotation of Xaa. A consequence of this interaction is the enhanced stability of the Pro-cisPro conformer in Ac-Pro-Pro-Xaa-NH(2) when Xaa is aromatic. The free energies associated with trans to cis transformation of the Pro-Pro moiety are 0.35, 0.59, 0.64, and 0.82 kcal/mol when Xaa is Tyr, Trp, Phe, and His (pH of 8.4), respectively. In comparison, the corresponding free energy is ～1.55 kcal/mol when Xaa is nonaromatic. The observed population of Pro-cisPro-His and the pH-induced perturbation of electron density of the His side chain were correlated, providing further evidence for a direct role of CH···π interaction in modulating the stability of Pro-cisPro population in Ac-Pro-Pro-Aro-NH(2). Our study establishes Pro-Pro-Aro to be a new sequence motif that can stabilize Pro-cisPro peptide bonds. This study not only identifies a new structurally biased sequence motif but also directly demonstrates the role played by CH···π interactions in subtly altering conformational preferences of three-residue peptide sequences with implications on the role played by cis-peptide bonds in unfolded proteins.     

Isomer- and species-selective infrared spectroscopy of jet-cooled 7H- and 9H-2-aminopurine and 2-aminopurine·H2O clusters

The infrared (IR) spectra of the supersonic-jet cooled 9H- and 7H-tautomers of 2-aminopurine (2AP) and of the 9H-2-aminopurine·H(2)O monohydrate clusters have been measured by mass- and species-selective IR-UV double resonance spectroscopy in the 3200-3900 cm(-1) region, covering the N-H and O-H stretching vibrations. The spectra are complemented by density functional (B3LYP and PW91) and by second-order M?ller-Plesset (MP2) calculations of the electronic energies and vibrational frequenciesof the respective 2AP tautomers and clusters. The 9H- and 7H-2-aminopurine tautomers were definitively identified by the shifts of their NH and NH(2) symmetric and asymmetric stretching frequencies and by comparison to the B3LYP/TZVP calculated IR spectra. The H-bond topologies of the two previously observed 9H-2-aminopurine·H(2)O isomers (Sinha. R. K.; et al. J. Phys. Chem. A2011, 115, 6208) are definitively identified as the "sugar-edge" isomer A and the "trans-amino-bound" isomer B by comparing their IR spectra to the calculated frequencies and IR intensities of the cluster isomers A, B, C, and D, as well as to the IR spectrum of 9H-2AP. The sugar-edge isomer A involves N9-H···OH(2) and HOH···N3 hydrogen bonds and is predicted to be the most stable form. The amino-bound isomer B involves NH(2)···OH(2) and HOH···N1 hydrogen bonds and is calculated to lie 2.5 kJ/mol above isomer A. The H-bond topology of the "cis-amino-bound" isomer C is symmetrically related to isomer B, with a hydrogen bond to the N3 of the pyrimidine group. However, it is calculated to lie 7 kJ/mol above isomer A and indeed is not observed in the supersonic jet. Isomer D involves a single H-bond to the N7 position, is predicted to be 14 kJ/mol above A and is therefore not observed.     

Structural characterization of the 1-butyl-3-methylimidazolium chloride ion pair using ab initio methods

Ab initio theoretical methods are used to investigate the gas-phase ion pairs of the ionic liquid 1-butyl-3-methylimidazolium chloride. Multiple stable conformers with the chloride anion positioned (in-plane) around the imidazolium ring or above the C2-H bond are determined. The relative energy ordering of the conformers is examined at the B3LYP, MP2, and CCSD(T) levels. Zero-point energies, BSSE, and basis set effects are examined. For accurate results, correlation (dispersion) effects must be included. The most stable conformers are essentially degenerate and have the chloride H-bonding to, or lying above, the C2-H bond. Other conformers are found to lie approximately 30 and approximately 60 kJ mol(-1) higher in energy. Results are compared with those from recent simulations and experimental studies. The effect of the chloride anion on rotation of the butyl chain is investigated and found to lower some rotational barriers while enhancing others. The origin of the rotational barriers is determined. The number and type of hydrogen bonds formed between the imidazolium cation and chloride anion is found to vary significantly among conformers. No evidence of a possible intra C(alkyl)-H...pi interaction is obtained; however, hints of a Cl...pi interaction are found. The vibrational spectrum of each conformer is examined, and the origin of multiple (H-bonding) features in the vibrational spectrum of the ionic liquid explained.     

CH···O hydrogen bonds in "clicked" diketopiperazine-based amide rotaxanes

Two amide [2]rotaxanes were synthesized in high yields using a novel N,N'-dipropargyl diketopiperazine axle centerpiece as the template to which the stoppers are attached through "click chemistry". (1)H and 2D NMR spectra provide evidence for two different H-bonding motifs, in one of which the triazole CH groups form C-H···O═C bonds with the wheel carbonyl O atoms. This motif can be controlled and switched reversibly by competitive anion binding.     

9Mg(OH)(2)·MgCl(2)·4H(2)O, a high temperature phase of the magnesia binder system

The metastable phase 9Mg(OH)(2)·MgCl(2)·4H(2)O (9-1-4 phase) was found at the extended metastable isotherm of Mg(OH)(2) in the system MgO-MgCl(2)-H(2)O at 120 °C and occurs as intermediate binder phase during setting of magnesia cement due to temperature development of the setting reaction. The crystal structure of the 9-1-4 phase was solved from high resolution laboratory X-ray powder diffraction data in space group I2/m (C2/m) (a = 22.2832(3) ?, b = 3.13501(4) ?, c = 8.1316(2) ?, β = 97.753(1)°, V = 562.86(2) ?(3), and Z = 1). Structural and characteristical relations of the phases in the system MgO-MgCl(2)-H(2)O can be derived, with which the development of the cement or concrete qualities becomes explainable.     

Existence of both blue-shifting hydrogen bond and Lewis acid-base interaction in the complexes of carbonyls and thiocarbonyls with carbon dioxide

In this study, 16 gas phase complexes of the pairs of XCHZ and CO(2) (X = F, Cl, Br; Z = O, S) have been identified. Interaction energies calculated at the CCSD(T)/aug-cc-pVTZ//MP2/aug-cc-pVTZ level including both BSSE and ZPE corrections range from -5.6 to -10.5 kJ mol(-1) for XCHOCO(2) and from -5.7 to -9.1 kJ mol(-1) for XCHS···CO(2). Substitution of one H atom by one halogen in formaldehyde and thioformaldehyde reduces the interaction energy of XCHZ···CO(2), while a CH(3) substitution increases the interaction energy of both CH(3)CHO···CO(2) and CH(3)CHS···CO(2). NBO and AIM analyses also point out that the strength of Lewis acid-base interactions decreases going from >C1=S3···C6 to >C1=O3C6 and to >C1-X4···C6. This result suggests the higher capacity of solubility of thiocarbonyl compounds in scCO(2), providing an enormous potential application for designing CO(2)-philic materials based on the >C=S functional group in competition with >C=O. The Lewis acid-base interaction of the types >C=S···C, >C-Cl···C and >C-Br···C is demonstrated for the first time. The contribution of the hydrogen bonding interaction to the total interaction energy is larger for XCHS···CO(2) than for XCHO···CO(2). Upon complexation, a contraction of the C1-H2 bond length and a blue shift of its stretching frequency have been observed, as compared to the isolated monomer, indicating the existence of a blue-shifting hydrogen bond in all complexes examined. Calculated results also lend further support for the viewpoint that when acting as proton donor, a C-H bond having a weaker polarization will induce a stronger distance contraction and frequency blue shift upon complexation, and vice versa.     

1-H2N-CB11F11]---synthesis and reactions of a functionalized fluorinated carbadodecaborate anion

In anhydrous hydrogen fluoride, K[1-H2N-CB11H11] is fluorinated with elemental fluorine to produce K[1-H2N-CB11F11]. Under strong alkaline conditions, two fluorine atoms of the [1-H2N-CB11F11]- anion are regioselectively exchanged, yielding the [1-H2N-4,6-(HO)2-CB11F9]- anion via [1-H2N-6-HO-CB11F10]- as an intermediate. Both hydroxycarborate anions were isolated as [Ph4P]+ salts. All of the species were characterized by IR, Raman, and multi-NMR spectroscopy, thermal analysis (DSC) as well as by mass spectrometry (MALDI). The assignment of the NMR signals was supported by DFT calculations. Solid-state structures of K[1-H2N-CB11F11], [BzPh3P][1-H2N-CB11F11], [Ph4P][1-H2N-4,6-(HO)2-CB11F9], [Ph4P][1-H2N-6-HO-CB11F10], and [BzPh3P][1-H2N-CB11H11] were determined by single-crystal X-ray diffraction.