Solution NMR studies of supramolecular complexes of [60]- and [70]fullerenes with mono O-substituted calix[6]arene

Supramolecular complexation of [60]- and [70]fullerenes with 37-allyl-38,39,40,41,42-pentahydroxy-5,11,17,23,29,35-hexa(4-tert butyl)calix[6]arene (I) has been studied in CCl(4) medium by NMR spectrometric method. All of the complexes are found to be stable with 1:1 stoichiometry. Formation constants (K) of the above supramolecular complexes have been determined from systematic variation of NMR chemical shifts of specific protons of I in the presence of [60]- and [70]fullerenes. Trends in the K value suggest that [70]fullerene binds more strongly with I relative to [60]fullerene. Both PM3 and ab initio calculations reveal that the intermolecular interaction in the [70]fullerene/I complex proceeds through quite deep energy minima.     

Energies of charge transfer and supramolecular interactions of some mono O-substituted calix[6]arenes with [60]fullerene by absorption spectrometric method

Equilibria for the formation of supramolecular complexes of [60]fullerene with a series of mono O-substituted calix[6]arenes, namely: (i) 37-methoxy-38,39,40,41,42-pentahydroxy-5,11,17,23,29,35-hexa(4-tert-butyl)calix[6]arene (1), (ii) 37-allyl-38,39,40,41,42-pentahydroxy-5,11,17,23,29,35-hexa(4-tert-butyl)calix[6]arene (2), (iii) 37-phenacyl-38,39,40,41,42-pentahydroxy-5,11,17,23,29,35-hexa(4-tert-butyl)calix[6]arene (3), (iv) 37-ethylester-38,39,40,41,42-pentahydroxy-5,11,17,23,29,35-hexa(4-tert-butyl)calix[6]arene (4) and (v) 37-benzyl-38,39,40,41,42-pentahydroxy-5,11,17,23,29,35-hexa(4-tert-butyl)calix[6]arene (5) have been studied in CCl4 medium by absorption spectroscopic technique. The stoichiometry has been found to be 1:1 ([60]fullerene:calix[6]arene) in each case. An absorption band due to charge transfer (CT) transition is observed in each case in the visible region. The vertical ionisation potentials (I(D)(v)) of all the calix[6]arenes under study have been estimated utilising CT transition energy. The experimental I(D)(v) values also yield a good estimate of the electron affinity of [60]fullerene. The degrees of CT in the ground state of the complexes have been found to be very low (about 0.15%). Resonance energy of the complexes have been estimated. Thermodynamic parameters for the supramolecular complex formation of [60]fullerene with mono O-substituted calix[6]arene receptors are reported. It is observed that among the calix[6]arenes under the present study, only 1 and 4 form inclusion complexes with [60]fullerene. This has also been substantiated by theoretical calculation using PM3 method. Thus presence of one substituent group (of different types) on the lower rim of the calix[6]arene molecule has been shown to govern the host-guest complexation process.     

Supramolecular interactions of [60]- and [70]fullerenes with calix[n]arenes

[60]- and [70]fullerenes have been shown to form 1:1 supramolecular complexes with (i) 24,26-dimethoxy-25,27-dihydroxy-5,11,17,23-tetra(4-tert-butyl)calix[4]arene (1) and (ii) 37,39,41-trimethoxy-38,40,42-trihydroxy-5,11,17,23,29,35-hexa(4-tert-butyl)calix[6]arene (2) in CCl(4) medium by absorption spectroscopy. Charge transfer absorption bands of the complexes have been located in each of the cases (except [70]fullerene-2 complex) studied from which the vertical ionisation potential of 1 has been obtained. Formation constants of the complexes have been determined at four different temperatures from which the enthalpies and entropies of formation of the complexes have been obtained. Moreover, the formation constant of [70]fullerene-2 complex is higher than that of the [60]fullerene-1 and [60]fullerene-2 complexes at all the four temperatures studied. This has been accounted in terms of greater cavity size of 2 which is a calix[6]arene compared to 1 which is a calix[4]arene and also by the fact that a high degree of preorganisation takes place in case of 2 through intramolecular H-bonding at its lower rim.     

Theoretical Studies on the Intermolecular Interactions of Aza-calix[2]arene[2]-triazines with RDX

Six fully optimized structures of the aza-calix[2]arene[2]-triazines/RDX supramo-lecular complexes have been obtained at the DFT-B3LYP/6-311++G** level,and the corresponding intermolecular interactions have been investigated using the B3LYP,mPWPW91 and MP2 methods at the 6-311++G** level,respectively.The natural bond orbital(NBO) and atoms in molecules(AIM) analyses have been performed to reveal the origin of interactions.To our interest,the result indicates that the strongest interaction is up to -22.34 kJ/mol after basis set superposition error(BSSE) and zero point energy(ZPE) correction at the MP2/6-311++G** level.Furthermore,the intermolecular interactions between aza-calix[2]arene[2]-triazines with the substituted amidos and RDX are stronger than those of other complexes.Thus,the complexes with amidos can be used as the candidates to increase the stability of explosive and eliminate the explosive wastewater.     

Density Functional Theory Studies on the Intermolecular Interactions of Five Aza-calix [6] arene Host with HMX

Five fully optimized structures of complexes between aza-calix[6]arene host monomers(Ma～Me) and complexes(a～e) have been obtained at the B3LYP/6-31G(d) level.Natural bond orbital(NBO) analysis was performed to reveal the origin of the interaction.The intermolecular interaction energy was evaluated with basis set superposition error correction(BSSE) and zero point energy correction(ZPEC).The B3LYP/6-31G(d) calculations on the five complexes have shown that the greatest interaction(-13.98 kJ/mol) is found in the complex between HMX and hexa-aza-calix[3]-p-tri-arene[3]-2-amido-1,3,5-tri-azine.The results have indicated that intermolecular interaction energies of aza-calix[6]arenes with substituted group are stronger than those without substituted group,and those with amido are greater than with nitryl.Thus,hexa-azacalix[3]-p-tri-arene[3]-2-amido-1,3,5-tri-azine is rather equal to eliminate HMX from explosive waste water.     

An Interesting Approach to Bis-calix[5]arene Analogue from Calix[6]arene

Calix [n] arenas {n = 4, 6 or 8} are easily prepared from formaldehyde and para-substituted phenols via cyclic condensation under alkaline conditions in one step. It is not surprising that the calyx [n] arene (n = 4, 6, 8) chemistry has been developing very rapidly during the latest 20 years1. However, it is not the case for calixarenes with odd benzene rings (for example, n = 5). The yield of p-tert-butylcalix [5] arene synthesized in one-step from p-tert-butylphenol and formaldehyde was a…     

双层夹心膜电极电位法测定溶剂聚合物膜中杯芳烃-金属离子配合物的生成常数

以双层夹心膜电极为指示电极,采用电位法测定了聚合物膜中活性离子载体杯[6]芳烃乙酯与金属离子形成的配合物的生成常数.提出了一种新的测定夹心膜膜电位的方法,由测得的膜电位可计算出配合物的生成常数.以杯[6]芳烃乙酯为离子载体,测得其与Li⁺,Na⁺,K⁺,Cs⁺和NH⁺₄等离子的配合物生成常数的对数值分别为6.14,6.48.6.74,7.43和6.21.制备了以Cs⁺为主离子的选择性电极,采用固定干扰法,测得对Li⁺,Na⁺,K⁺和NH⁺₄等离子的选择性系数的对数值分别为-3.33,-2.54,-1.6和-2.9.实验结果表明,配合物的生成常数与选择性系数之间有较好的相关性.生成常数越大,电极对相应离子的选择性越高.     

Synthesis and structure of a novel molybdenum imido calix[6]arene

Treatment of p-tert-butylcalix[6]areneH₆ (H₆L) with [Mo(OBu^t)₂{[2,2′-(N)-C₆H₄]₂(CH₂CH₂)}] in refluxing toluene affords, after work-up, the complex [Mo(2-NC₆H₄CH₂CH₂C₆H₄NHC(Me)NH-2^/)LH₂]·4MeCN (1), which contains an 11-membered metallocyclic ring as characterised by Synchrotron X-radiation.     

Charge Transfer in the Electron Donor-Acceptor Complexes of [60]Fullerene/PM567 and [70]Fullerene/PM567

UV-Vis spectroscopic investigations of electron donor-acceptor complexes of [60]- and [70]fullerenes with a well-known laser dye, viz., 4,4-difluoro-1,3,5,7,8-pentamethyl-2,6-diethyl-4-bora-3a,4a-diaza-s-indecene (PM567), are reported in toluene solutions. Absorption bands due to charge transfer (CT) transitions have been located in the visible region. The vertical ionization potential of PM567 has been determined utilizing Mulliken’s equation. A possible mechanism for the interaction between the electronic subsystems of [60]- and [70]fullerenes with PM567 is discussed. Oscillator strengths, resonance energies and electronic coupling elements of the CT complexes were estimated. Formation constant data and ab initio calculations suggest that PM567 binds more tightly with [60]fullerene compared to [70]fullerene.     

三桥联杯[6]酰腙衍生物和相关化合物的合成

以杯[6]芳烃和杯[6]-1,4-冠-4为起始原料,经过醚化引入酯基,接着用水合肼肼解得到杯[6]酰肼衍生物2和6,然后再与水杨醛进行缩合反应,高产率合成了两例杯[6]酰腙衍生物3和7.化合物6与2倍的二水杨醛乙二醚进行"1+2"缩合反应,得到了一例新型结构的杯[6]-1,4-2,6-3,5-三桥联酰腙衍生物8,产率73%.新化合物2,3,6,7和8的结构经元素分析、红外光谱、质谱、核磁共振谱等证实.     

Absorption spectrophotometric study of supramolecular complexation of [60]- and [70]fullerenes with 24,26-dimethoxy-25,27-dihydroxy calix[4]arene

Supramolecular interactions of 24,26-dimethoxy-25,27-dihydroxy calix[4]arene (1) with [60]- and [70]fullerenes have been studied in only chloroform and in a ternary solvent mixture comprising of chloroform, ethyl alcohol and toluene by UV-vis absorption spectrophotometric method. The experimental results are explained using the model that takes into account the interaction between electronic subsystems of 1 and fullerene. The most interesting feature is the preference of [60]fullerene over [70]fullerene for 1 in ternary solvent mixture as revealed by higher value of formation constant of [60]fullerene/1 complex. The selectivity towards [60]fullerene opens up the way toward self-assembling systems and new separation and purification methods for fullerenes.     

Phosphate Doubly Capped Tetrahomodioxacalix[6] arene

A bisphosphate-bridged tetrahomodioxacalix[6] arene with a C2v symmetry at the ambient temperature was obtained by the reaction of tetrahomodioxacalix[6] arene with POCl3。     

Enhanced head-to-head photodimers in the photocyclodimerization of anthracenecarboxylic acid with a cationic pillar[6]arene

The complexation behaviors of anthracenecarboxylic acid and water-soluble cationic pillararenes have been investigated by ¹H NMR, UV-vis and ITC methods. The cationic pillar[6]arene was found to stepwise form 1:1 and 1:2 complexes, having a large K₁ and a relatively small K₂ values. Photocyclodimerization of AC within the pillar[6]arene improved the yield of the head-to-head photodimers. Up to 4.97 HH/HT ratio has been reached by optimizing the reaction conditions.     

Cucurbit[5]uril, Decamethylcucurbit[5]uril and Cucurbit[6]uril. Synthesis, Solubility and Amine Complex Formation

A simple way to prepare cucurbit[5]uril is described. The macrocycles of the cucurbituril type are nearly insoluble in water. The solubilities of cucurbit[5]uril, decamethylcucurbit[5]uril and cucurbit[6]uril in hydrochloric acid, formic acid and acetic acid of different concentrations have been investigated. Due to the formation of complexes between cucurbit[n]urils and protons the solubility increases in aqueous acids. The macrocyclic ligands are able to form complexes with several organic compounds. Thus, the complex formation of the cucurbituril macrocycles with different amines has beenstudied by means of calorimetric titrations. The reaction enthalpy gives noevidence of the formation of inclusion or exclusion complexes. ¹H-NMR measurements show that in the case of cucurbit[5]uril and cucurbit[6]uril the organic guest compound is included within the hydrophobic cavity. Decamethylcucurbit[5]uril forms only exclusion complexes with organicamines. This was confirmed by the crystal structure of the decamethylcucurbit[5]uril-1,6-diaminohexane complex.     

A comparative study of molecular complexation of [60]- and [70]fullerenes with 1,3,5-tribromobenzene by UV-vis spectrophotometric method

By UV-vis spectrophotometric method it has been shown that 1,3,5-tribromobenzene (TBB) forms molecular complexes of 1:2 stoichiometry with [60]- and [70]fullerenes. An isosbestic point could be detected in case of the [70]fullerene complex. The formation constant of the [60]fullerene complex is higher than that of the [70]fullerene complex at each of the four temperatures under study. This is in opposite order of the electron affinities of the two fullerenes; moreover, no charge transfer band was observed in the spectra of either complex in solution. This indicates that van der Waals forces, rather than CT interactions, are responsible for complexation. The results reveal that the C-atoms at the pentagon vertices of [60]fullerene have greater polarizing power than those in [70]fullerene.     

Synthesis of Schiff Base Calix [4] arene Crowns

This letter reports the synthesis of Schiff base calix [4] arene crowns containing m-xylylene phenol subunit, in which calix [4] arene Schiff base crowns 2a,2b and 2c were formed by 1:1 condensation of calix [4] arene diamine 1 with dialdehydes (2,6-diformyl-4-chlorophenol 3a,2,6-diformyl-4-methylphenol 3b,2,6-diformyl-4-tert-butylphenol 3c)under high dilute condition in refluxing anhydrous ethanol in 65-70% yield.     

Fullerene encapsulation with calix[5]arenes

This paper presents the synthesis of the fullerene hosts based on the calix[5]arenes and their binding properties. Calix[5]arenes 1a, 2, 3a bind C₆₀ or C₇₀ in organic solvents. The solvent effect of the fullerene complexation was clearly observed; the association constant decreases in a solvent with high solubility for C₆₀. Covalently linked double-calix[5]arenes 4-6 were also investigated on their binding properties for fullerenes in organic solvents. Their binding abilities for both C₆₀ and C₇₀ are extremely high in toluene solution. Higher binding selectivity toward C₇₀ is observed by all the double-calix[5]arenes. The selectivity of 5a toward C₇₀/C₆₀ is highest in toluene with a value of 10. The structures of the supramolecular complexes of the calix[5]arene hosts and C₆₀ or C₇₀ were investigated by using ¹H and ¹³C NMR studies. The molecular mechanics calculation and X-ray structure reveal that the interior of the calix[5]arene is complementary to the exterior of C₆₀ molecule. In contrast, the host-guest complexes of C₇₀ with the simple calix[5]arenes take many conformational options due to its less symmetric shape. The molecular mechanics calculation and our chemical shift simulation nicely worked to estimate the reliable structures; the calix[5]arene cavity takes up C₇₀ molecule, and the C₇₀ molecule tilts significantly from the C5 axis of the calix[5]arene. In the case of the host-guest complex of C₇₀ with the double-calix[5]arene, the molecular dynamics simulation of the host-guest complex represented the realistic movement of the bound C₇₀ inside the cavity. The combination of the molecular dynamics simulation and the chemical shift simulation of the host-guest complex suggested that the C₇₀ molecule rapidly moves inside the cavity.     

Energies of Charge Transfer for the Supramolecular Complexes of [60]- and [70]Fullerenes with a Series of meso-Tetraphenylporphyrins in the Solution State

Supramolecular complexes of [60]- and [70]fullerenes with various meso-tetraphenylporphyrins in toluene solutions have been studied by electronic absorption spectroscopy. Charge transfer (CT) absorption bands are observed in the visible region. Vertical ionization potentials (I _D ^V) of the meso-tetraphenylporphyrins are reported from a study of EDA interaction of these porphyrins with a number of electron acceptors like o-chloranil, p-chloranil, 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) and vitamin K. The dependence of the CT transition energy on the donor ionization potential has been utilized to estimate the vertical electron affinities (E _A ^V) of [60]- and [70]fullerenes in solution. The value of E _A ^V for [60]fullerene is found to be 0.10 eV lower in magnitude than that of [70]fullerene. We have extracted degrees of CT, and oscillator and transition dipole strengths of the fullerenes/meso-tetraphenylporphyrins complexes. The experimental results show that the CT complexes studied here have a neutral character in their ground states. Electronic coupling elements have been determined for fullerene/meso-tetraphenylporphyrin complexes. Values of the solvent reorganization energy indicate that the electron transfer process takes place at a faster rate in the case of [70]fullerene/meso-tetraphenylporphyrin complexes.     

基于C3v对称性的杯[6]芳烃对Hg2+的荧光选择性识别

合成了一系列具有C3v对称性、下缘分别利用Se、Te和S杂原子连接蒽环发光基团的杯[6]芳烃衍生物1-3.通过紫外-可见光谱和荧光光谱研究了它们对各种碱金属离子和过渡态金属离子的化学传感识别行为. 结果表明,含有Se杂原子的主体1在CH2Cl2溶液中对Hg2+表现出良好的选择性. 并且,通过肉眼可以直接观察到溶液颜色由无色变为黄色.通过荧光光谱的连续滴定实验,主体1-Hg2+体系的稳定常数可达（1.12 ? 0.08) ? 105 M-1. 因此,化合物1有望成为一种用于检测Hg2+的新型化学传感器.     

NMR spectrometric study of molecular complex formation of [60]- and [70]fullerenes with a number of phosphine oxides

Molecular complex formation between [60]- and [70]fullerenes with a series of phosphine oxides, namely, tri-n-octyl phosphine oxide, triphenyl phosphine oxide and tri-n-butyl phosphine oxide has been studied in CCl4 medium by NMR spectrometric method. Both [60]- and [70]fullerenes have been shown to form 1:1 adducts with the above series of phosphine oxides. Formation constants (K) for all the complexes have been determined from the systematic variation of NMR chemical shifts of specific protons of the donors in presence of [60]- and [70]fullerenes. Trends in the values of K suggest that [70]fullerene binds stronger with the phosphine oxides relative to [60]fullerene.