Titanium and zirconium complexes of a phosphorus-containing p-tert-butylcalix[5]arene ligand: importance of metal and conformation on ligand/metal binding

Binding of a calix[5]arene containing a single phosphorus ligand and three hydroxyl groups, calix[5]PNMe2(OH)3, 1, toward titanium and zirconium is investigated to yield insight into the factors that determine the strength of the phosphorus/metal interaction within the constraint of the calix[5]arene. Treatment of 1 with tetrakis(dimethylamino)titanium yields three complexes, 4a, 4b, and 4c, each of which shows the loss of 3 mol of dimethylamine in the reaction with the titanium bound to three oxygens. Treatment of 1 with tetrakis(diethylamino)zirconium proceeds similarly, although only two products, 5a and 5b, were isolated. X-ray structures of the products were obtained. Complexes 4a and 5a show similar geometries, with the calix[5]arene in an approximate cone conformation and the phosphorus lone pair directed toward the metal. The P...M distances are, however, markedly different: 3.69 A in 4a and 3.18 A in 5a, the former indicative of no interaction and the latter a weak one. Complexes 4b and 5b each are dimers, featuring a planar four-membered M-O-M-O ring; however, the titanium is five-coordinate in 4b with no phosphorus/metal bond, while the zirconium in 5b is six-coordinate with a P-Zr distance of 2.95 A. Complex 4c is monomeric with the calix[5]arene in an approximate 1,2-alternate conformation with a P...Ti distance of 2.90 A. The two most significant aspects controlling the phosphorus/metal contact are the metal, with the larger zirconium showing stronger interaction, and the calix[5]arene conformation, with the cone conformation showing the weaker interaction.     

2:1 Ba/Ti(IV) heterobimetallic complex based on two calix[6]arenes

Reaction of p-Bu(t)-calix[6]arene with barium metal in methanol then [Ti(OPr(i))4] affords a heterobimetallic complex with a central Ti(IV) attached to two calix[6]arenes in the 1,3-alternate conformation, each with an endo-barium sharing common phenolate groups with the titanium centre.     

Structure and conformational equilibrium of thiacalix[4]arene by density functional theory

Density functional theory calculations for the structure and conformational equilibrium of thiacalix[4]arene are reported. The conformational equilibrium of thiacalix[4]arene, a heterocalixarene in which the phenol groups are bridged by sulphur atoms is compared to the conformational equilibrium of calix[4]arene. Thiacalix[4]arene conformational energies relative to the cone conformer (ΔE's) are reduced in comparison with calix[4]arene. This conformational change is in qualitative agreement with recent NMR spectroscopy measurements of the conformational equilibrium for a tetraethylether of thiacalix[4]arene in a CDCl₃ solution which indicates an enhanced chemical exchange of thiacalixarene conformers in comparison with similar methylene bridged structures. Density functional theory results for the structure of thiacalix[4]arene are in good agreement with recent X-ray diffraction measurements. The electrostatic potentials in the cone conformers of thiacalix[4]arene and calix[4]arene suggest that their complexation or recognition abilities can be significantly different. Dipole moments of the four thiacalix[4]arene conformers are in the order: cone>1,2-alternate>partial-cone>1,3-alternate.     

Highly regioselective [2+2+2] cycloaddition of terminal alkynes catalyzed by titanium complexes of p-tert-butylthiacalix[4]arene

Mono- and dinuclear titanium complexes of p-tert-butylthiacalix[4]arene were applied as a catalyst for [2+2+2] cycloaddition of terminal alkynes. They showed high catalytic activity and regioselectivity toward 1,3,5-trisubstituted benzenes over 1,2,4-trisubstituted isomers. The regioselectivity was rationalized in terms of the steric effect of the thiacalixarene skeleton and the coordination of the bridging sulfur atom to the titanium center.     

含酰胺和席夫碱单元的杯[4]芳烃衍生物的合成与配合性能

杯[4]-1,3-二乙酸乙酯衍生物1与水合肼反应生成杯[4]芳烃酰肼衍生物2, 然后进一步与相应的芳醛反应, 高产率地合成了三个新型的含酰胺和席夫碱单元的杯[4]芳烃衍生物3a～3c和一例新型杯[4]冠醚4. 阳离子萃取实验表明新型杯芳烃衍生物比只含有酰胺基或席夫碱基的杯芳烃衍生物有更强的软金属离子配合性能, 杯[4]冠醚4还对Ag^＋有较好的选择性萃取能力.     

Synthesis and crystal structure of uranium(IV) complexes with calix[n]arenes (n = 4, 6 and 8): mononuclear, polynuclear and 1D polymeric species

Reactions of UCl4 with calix[n]arenes (n = 4, 6) in THF gave the mononuclear [UCl2(calix[4]arene - 2H)(THF)2].2THF (.2THF) and the bis-dinuclear [U2Cl2(calix[6]arene - 6H)(THF)3]2.6THF (.6THF) complexes, respectively, while the mono-, di- and trinuclear compounds [Hpy]2[UCl3(calix[4]arene - 3H)].py (.py), [Hpy](4)[U2Cl6(calix[6]arene - 6H)].3py (.3py), [Hpy]3[U2Cl5(calix[6]arene - 6H)(py)].py (.py) and [Hpy]6[U3Cl11(calix[8]arene - 7H)].3py (.3py) were obtained by treatment of UCl4 with calix[n]arenes (n = 4, 6, 8) in pyridine. The sodium salt of calix[8]arene reacted with UCl4 to give the pentanuclear complex [U{U2Cl3(calix[8]arene - 7H)(py)5}2].8py (.8py). Reaction of U(acac)4 (acac = MeCOCHCOMe) with calix[4]arene in pyridine afforded the mononuclear complex [U(acac)2(calix[4]arene - 2H)].4py (.4py) and its treatment with the sodium salt of calix[8]arene led to the formation of the 1D polymer [U2(acac)6(calix[8]arene - 6H)(py)4Na4]n. The sandwich complex [Hpy]2[U(calix[4]arene - 3H)2][OTf].4py (.4py) was obtained by treatment of U(OTf)4 (OTf = OSO2CF3) with calix[4]arene in pyridine. All the complexes have been characterized by X-ray diffraction analysis.     

杯芳烃与NO2硝化反应的研究

系统地研究了羟基杯[n]芳烃、甲氧基杯[n]芳烃和对特丁基杯[n]芳烃(n＝4, 6, 8)与NO₂气体的硝化反应, 发现可以成功地得到25,26,27,28-四羟基杯[4]芳烃、37,38,39,40,41,42-六羟基杯[6]芳烃以及25,26,27,28-四甲氧基杯[4]芳烃的对位全硝化产物, 产率分别为90%, 70%和40%; 尤其是25,26,27,28-四羟基杯[4]芳烃与NO₂的反应20 min即可完成. 认为共振式酚氧负离子结构是影响该类硝化反应的关键, 并对反应机理进行了探讨.     

碱金属掺杂叔丁基杯[4]芳烃体系的结构及非线性光学性质

采用密度泛函理论B3LYP方法得到了M@t-Bu-calix[4]arene和(M@t-Bu-calix[4]arene)Li′(M=Li,Na,K)体系的几何结构.其中(M@t-Bu-calix[4]arene)Li′(M=Li,Na,K)三个体系各有5个稳定异构体,在前三个异构体中,碱金属与t-Bu-calix[4]arene分子间具有很强的相互作用能,说明了体系的稳定性.在部分(M@t-Bucalix[4]arene)Li异构体中Li′原子以阴离子形式存在,整个体系表现出碱金属化物的特性.此外,使用CAMB3LYP方法计算了t-Bu-calix[4]arene及碱金属掺杂后体系的非线性光学性质.结果表明,t-Bu-calix[4]arene内部掺杂一个碱金属原子M后,体系的一阶超极化率(β0)有较大提高,而在配体外部又掺杂一个Li原子后,体系具有更大的β0值.其中(M@t-Bu-calix[4]arene)Li′体系的MLi′-4异构体表现出最高的β0值(41827-114354 a.u.),并且随着M原子序数的增加而逐渐增大.可见,碱金属掺杂是提高t-Bu-calix[4]arene非线性光学响应的一种有效策略.     

High-performance Liquid Chromatography Study of the Nitration Course of Tetrabutoxycalix[4]arene at the Upper Rim:Determination of the Optimum Conditions for the Preparation of 5,11,17-Trinitro-25,26,27,28-tetrabutoxycalix[4]arene

A selective nitration of calix[4]arene at the upper rim in one pot process was described by monitoring the time dependence of the distribution of products by high‐performance liquid chromatography (HPLC). The discrimination of five nitrated products was accomplished by molecular symmetry considerations and ¹H NMR analysis. As a result, unusual 5,11,17‐trinitrocalix[4]arene ( 2d ) was obtained in 57% isolated yield. 5,11‐Dinitro‐calix[4]arene ( 2b ) and 5,11,17‐trinitrocalix[4]arene ( 2d ) with tetranitrocalix[4]arene 2e were further characterized by crystal X‐ray diffraction analysis. Furthermore, as an example of potential application, trinitrocalix[4]arene 2d could be converted to triaminocalix[4]arene 3d conveniently.     

Band intensity in the IR spectra and conformations of calix[4]arene and thiacalix[4]arene

The experimental IR and Far IR spectra of the calix[4]arene, p-tert-butylcalix[4]arene, thialcalix[4]arene and p-tert-butylthiacalix[4]arene were examined at different temperatures and interpreted. The band frequencies and intensities in the IR spectra of the calix[4]arene and thialcalix[4]arene were calculated. The absorption curves of the four possible calix[4]arene conformations: cone, partial cone, 1,2- and 1,3-alternate were computed. The bands characteristic for each conformation are defined and assigned. The obtained spectra-structure correlation can be used for the characteristic of calixarenes conformation.     

含噻二唑官能基的对叔丁基硫桥杯[4]芳烃衍生物的合成及结构

以对叔丁基硫桥杯[4]芳烃(1)为原料, 在碳酸钾存在下与碘甲烷反应, 生成1,3-二取代桥杯[4]芳烃(2), 其分别与1,2-二溴乙烷, 1,3-二溴丙烷在碳酸钾的存在下进行烷基化反应, 生成硫桥杯[4]芳烃衍生物3和4. 在氢氧化钠存在下,其与过量的含不同官能团的2-巯基-1,3,4-噻二唑反应, 生成下缘含1,3,4-噻二唑基的硫桥杯[4]芳烃衍生物5a, 5b, 6a和6b, 并通过了¹H NMR, ¹³C NMR, IR, MS和元素分析的确证. 同时, X射线分析确定了硫桥杯[4]芳烃3和5a的晶体结构.     

Selective synthesis of conformationally restricted mono-cyclopentadienyl titanium(IV) complexes of p-tBu-calix[6]arene

Reaction of p-'Bu-calix[6]arene with potassium metal in methanol followed by [TiCp2Cl2] affords novel mononuclear and binuclear monocyclopentadienyl titanium(IV) complexes, both having the same inverted double cone conformation with a Cp in one of the cavities, in both complexes.     

A paradigm shift in the construction of heterobimetallic complexes: synthesis of group 2 & 4 metal-calix[6]arene complexes

Deprotonation of calix[6]arenes with barium in methanol followed by the addition of [Ti(OPr(i))(4)] or [Zr(OBu(n))(4)] is effective in the formation of novel dimeric 2:1 barium-titanium(IV)/zirconium(IV) calix[6]arene complexes. In these complexes a central Ti(IV)/Zr(IV) coordinated in the exo-position connects the two calix[6]arenes in the 1,3-alternate conformation, each with an endo-barium sharing common phenolate groups with the titanium/zirconium centre and participating in cation-pi interactions. A homometallic barium calix[6]arene dimer was also prepared wherein the calix[6]arenes are in the 1,3-alternate conformation with each coordinating one endo- and one exo-barium centre. The exo-barium cations connect the two calix[6]arenes through bridging methanol ligands. In this and the heterometallic complexes, cation-pi complexation of the Ba(2+) ion within the 1,3 alternate conformation of calix[6]arene facilitates the formation of the dimeric complexes in methanol. In contrast, the smaller Sr(2+) ion did not form similar complexes in methanol, and the formation of an analogous 2:1 strontium-titanium calixarene complex required the use of the more sterically demanding donor alcohol, isopropanol, the resulting complex being devoid of cation-pi interaction. The results show (i) that a subtle interplay of solvation strength, coordination array type and cavity/cation size influences the accessibility of heterobimetallic complexes based on calix[6]arenes, and (ii) a synergistic endo-exo binding behaviour.     

杯[4]芳烃黄原酸酯衍生物的合成与阳离子萃取性能

以二氧六环作溶剂, 杯[4]芳烃二甲氧基二羟乙氧基衍生物2与氢氧化钾、二硫化碳作用合成了杯芳烃黄原酸盐衍生物3, 并进一步与碘甲烷或氯化苄反应首次合成了含黄原酸酯基的杯芳烃衍生物4a和4b. 阳离子萃取试验表明该新型杯芳烃衍生物比单硫杂杯芳烃衍生物具有更好的过渡金属离子萃取性能.     

碱金属掺杂叔丁基杯[4]芳烃体系的结构及非线性光学性质

采用密度泛函理论B3LYP方法得到了M@t-Bu-calix[4]arene和（M@t-Bu-calix[4]arene）Li'（M=Li,Na,K）体系的几何结构. 其中（M@t-Bu-calix[4]arene）Li'（M=Li,Na,K）三个体系各有5个稳定异构体,在前三个异构体中,碱金属与t-Bu-calix[4]arene分子间具有很强的相互作用能,说明了体系的稳定性. 在部分（M@t-Bucalix[4]arene）Li异构体中Li'原子以阴离子形式存在,整个体系表现出碱金属化物的特性. 此外,使用CAMB3LYP方法计算了t-Bu-calix[4]arene及碱金属掺杂后体系的非线性光学性质. 结果表明,t-Bu-calix[4]arene内部掺杂一个碱金属原子M后,体系的一阶超极化率（β₀）有较大提高,而在配体外部又掺杂一个Li原子后,体系具有更大的β₀值. 其中（M@t-Bu-calix[4]arene）Li'体系的MLi'-4异构体表现出最高的β₀值（41827-114354 a.u.）,并且随着M原子序数的增加而逐渐增大. 可见,碱金属掺杂是提高t-Bu-calix[4]arene非线性光学响应的一种有效策略.     

含席夫碱和酰胺单元的新型双杯[4]芳烃的合成

对叔丁基杯[4]芳烃-1,3-二醛基衍生物2与对叔丁基杯[4]-1,3-二酰肼衍生物4在稀释条件下进行“1＋1”分子间缩合反应, 高产率地合成了含席夫碱和酰胺单元的新型双杯[4]芳烃衍生物5. 所有新化合物的结构经元素分析、质谱、核磁共振谱等表征证实, 杯[4]芳烃单元均为1,3-桥联且采取锥式构象.     

Metal-mediated self-assembly of pyridylcalixarenes: prevention of intramolecular metal chelation is essential in constructing molecular capsules.

To construct calixarene-based molecular capsules utilizing the pyridyl-Pd(II) interaction, reactions of cone-pyridylcalix[4]arene 3, cone-pyridylcalix[5]arene 13, and cone-pyridylcalix[4]arene bis-crown 16 with square-planar Pd(II) complex 7 were investigated. Because of the coexistence of intermolecular binding and chelate-forming intramolecular binding, the reactions of cone-pyridylcalix[4]arene 3 or cone-pyridylcalix[5]arene 13 with cis-Pd(II) complex 7 yield complicated, structure-unknown oligomers. The short dioxyethylene bridges on the lower rim of pyridylcalix[4]arene bis-crown 16 rigidify the cone conformation and thus prohibit 16 from the intramolecular binding with a metal component. Thus, two cone-tetrapyridylcalix[4]arene bis-crown 16 and four cis-Pd(II) complex molecules self-assemble into molecular capsules that exist as a parallel/antiparallel conformer mixture in a nearly 1:1 ratio. The results demonstrated that to prevent entropically favorable intramolecular binding is essential is constructing higher capsule-like structures with calixarene building blocks by self-assembling.     

Stilbene-bridged 1,3-alternate calix[4]arene crown ether for selective alkali ion extraction

A series of stilbene-bridged calix[4]arenes was synthesized through an intramolecular reductive McMurry coupling of bisbenzaldehyde calix[4]arene in high yields. Tetra- and pentaethylene glycol chains were tethered to the phenolic groups of calix[4]arene to form stilbene-bridged calix[4]arene crown-5 and crown-6, respectively. The presence of stilbene bridge over the calix[4]arene rim effectively prevented the connection of the polyether chains in the cone conformation resulting in the exclusive formation of 1,3-alternate stilbene-bridged calix[4]arene crown product. Compared to the cone analogues, the 1,3-alternate calix[4]arene crown ethers showed a greater extraction ability and selectivity toward Cs⁺.     

含苯并噁唑基的硫桥杯[4]芳烃衍生物的合成及结构

在碳酸钾存在下, 对叔丁基硫桥杯[4]芳烃(1)分别与端基二溴代烷和碘甲烷反应, 生成硫桥杯[4]芳烃衍生物2～4. 含端基溴代的硫桥杯[4]芳烃衍生物2和4分别与2-巯基苯并噁唑在碳酸钾存在下反应, 生成硫桥杯[4]芳烃衍生物5a～5d. 通过1H NMR, 13C NMR, IR, MS和元素分析等手段对产物进行了表征. 同时, X射线分析确定了硫桥杯[4]芳烃5b的晶体结构.     

Two organometallic fragments inclusioned in a 1,3-alternate calix[4]arene tetraphosphane: evidence for transition metal-arene interaction through the cavity

The preparation of an 1,3-alternate calix[4]arene tetraphosphane ligand, 25,26,27,28-tetrakis{2-(diphenylphosphino)ethoxy}calix[4]arene (4), is described. Ligand 4 is obtained in four steps in 17% overall yield. Reaction of 4 with AgBF4 produced the encapsulated two silver complex [Ag2{(P,P,P,P)-tetraphencalix[4]arene}](BF4)2. The solid-state structure shows that the encapsulated silver undergoes a substantial pi-interaction by two opposite arene rings. Rhodation of 4 employing [Rh(cot)2]BF4 yielded the encapsulated complex with a bent coordination mode. Two organometallic fragments inclusioned inside a 1,3-alternate calix[4]arene tetraphosphane was also achieved by the reaction of 4 with [PtH(PPh3)2 (thf)]+. Full characterization includes X-ray structural studies of compounds 4-6.