23296-29-9

Upstream product

• 914-45-4 tetra-n-butylammonium picrate 
• 88-89-1 2,4,6-Trinitrophenol 
• 13126-12-0 rubidium nitrate 

Relevant academic research and scientific papers

Ion Association. Comparison of Spectroscopic and Conductance Values of Association Constants

Molar conductances of potassium, rubidium, and cesium picrate and of cesium tetraphenylborate have been determined in 2-butanone at 25 deg C over a concentration range of 0.1-1.6 mmol L-1.These Λ,C data together with those for lithium and sodium already determined in this laboratory were fitted by using the Lee-Wheaton (LW), the Pitts (P), the Fuoss 78 (F), and the Justice (J) conductance equations to obtain values of ion association constants, KA, and limiting molar conductances.Spectrophotometric absorbance changes were measured for sodium and cesium picrate and remeasured for lithium and tetra-n-butylammonium picrate at 380 nm and 25 deg C over a concentration range of 0.02-1.4 mmol L-1.Values of the cesium-133 NMR chemical shifts of cesium picrate were determined over a concentration range of 0.1-3 mmol L-1 while those for cesium tetraphenylborate were determined over a range from 0.25 to 10 mmol L-1.We calculated values of ion assiciation constants for the various salts using this spectroscopic data.The values of KA determined spectroscopically and the values determined conductimetrically are the same within experimental error with one exception; for cesium tetraphenylborate, the NMR value depends on the concentration range of data included in the analysis.

Syntheses, crystal structures, thermal behaviors, and sensitivities of new initiator compositions: Rubidium salts of trinitrophenol and trinitroresorcinol

Three new polymeric Rb(I) salts of trinitrophenol and trinitroresorcinol, rubidium trinitrophenol ([RbTNP]n), bi-substituted rubidium salt of trinitroresorcinol ([Rb2TNR·H2O]n), and mono-substituted rubidium sal

Buckyball-Based Spherical Display of Crown Ethers for de Novo Custom Design of Ion Transport Selectivity

Searching for membrane-active synthetic analogues that are structurally simple yet functionally comparable to natural channel proteins has been of central research interest in the past four decades, yet custom design of the ion transport selectivity still remains a grand challenge. Here we report on a suite of buckyball-based molecular balls (MBs), enabling transmembrane ion transport selectivity to be custom designable. The modularly tunable MBm-Cn (m = 4-7; n = 6-12) structures consist of a C60-fullerene core, flexible alkyl linkers Cn (i.e., C6 for n-C6H12 group), and peripherally aligned benzo-3m-crown-m ethers (i.e., m = 4 for benzo-12-crown-4) as ion-transporting units. Screening a matrix of 16 such MBs, combinatorially derived from four different crown units and four different Cn linkers, intriguingly revealed that their transport selectivity well resembles the intrinsic ion binding affinity of the respective benzo-crown units present, making custom design of the transport selectivity possible. Specifically, MB4s, containing benzo-12-crown-4 units, all are Li+-selective in transmembrane ion transport, with the most active MB4-C10 exhibiting an EC50(Li+) value of 0.13 μM (corresponding to 0.13 mol % of the lipid present) while excluding all other monovalent alkali-metal ions. Likewise, the most Na+ selective MB5-C8 and K+ selective MB6-C8 demonstrate high Na+/K+ and K+/Na+ selectivity values of 13.7 and 7.8, respectively. For selectivity to Rb+ and Cs+ ions, the most active MB7-C8 displays exceptionally high transport efficiencies, with an EC50(Rb+) value of 105 nM (0.11 mol %) and an EC50(Cs+) value of 77 nM (0.079 mol %).

Synthesis, binding properties and theoretical studies of p-tert-butylhexahomotrioxacalix[3]arene tri(adamantyl)ketone with alkali, alkaline earth, transition, heavy metal and lanthanide cations

p-tert-Butylhexahomotrioxacalix[3]arene tri(adamantyl)ketone (1b) was synthesized for the first time. Compound 1b was obtained in a cone conformation in solution at room temperature, as established by NMR spectroscopy (1H and 13C). The binding properties of ligand 1b for alkali, alkaline earth, transition, heavy metal and lanthanide cations have been assessed by phase transfer and proton NMR titration experiments. Molecular mechanics and ab initio techniques were also employed to complement the NMR data. The results are compared to those obtained with other closely related homooxacalixarene derivatives. Although triketone 1b is a weak extractant, it shows a strong peak selectivity for Na+ and also some preference for Ag+. Proton NMR titrations indicate the formation of 1:1 complexes between 1b and the cations studied, and also that they should be located inside the cavity defined by the phenoxy and carbonyl oxygen atoms. Although the molecular mechanics results show little correlation with the NMR data, a good agreement was obtained with the ab initio models.

A study of C-F···M+ interaction: Alkali metal complexes of the fluorine-containing cage compound

The C-F···M+ interaction was investigated by employing a cage compound 1 that has four fluorobenzene units. The NMR (1H, 13C, and 19F) spectra and X-ray crystallographic analyses of 1 and its metal complexes showed clear evidence of the interaction. Short C-F···M+ distances (CF···K+, 2.755 and 2.727 A; C-F···Cs+ 2.944 and 2.954 A) were observed in the crystalline state of K+ ? 1 and Cs+ ? 1. Furthermore, the C-F bond lengths were elongated by the interaction with the metal cations. By calculating Brown's bond valence, it is shown that the contribution of the C-F unit to cation binding is comparable or greater than the ether oxygen in the crystalline state. Representative spectroscopic changes implying the C-F···M+ interaction were observed in the NMR (1H, 13C, and 19F) spectra. In particular, 133Cs-19F spin coupling (J = 54.9 Hz) was observed in the Cs+ complex.

Guest inclusion properties of calix[6]arene-based unimolecular cage compounds. On their high Cs+ and Ag+ selectivity and very slow metal exchange rates

The reaction of 1.3.5-tri-O-alkylated calix[6]arenes with 1,3,5- tris(bromomethyl)benzene yielded capped calix[6]arenes (2 with ten-butyl groups on the upper tim and 3 without tert-butyl groups) in unexpectedly high yields (80 - 91%). Combined studies of 2 and 3 by MM3 computation, X-ray analysis, and 1H NMR spectroscopy established that these calix[6]arenes feature a unique structure consisting of alternately-arranged three flattened mesitylene-linked phenyl units and three stand-up anisole units. Particularly, compound 2 possesses a closed ionophoric cavity: the upper hemisphere is closed by three ten-butyl groups of anisole units and the lower hemisphere is closed by a mesitylene cap and three anisole methoxy groups. The 1H NMR spectrum was scarcely changed at wide temperature range (30 ~ 130 °C), indicating that the structure is extremely rigidified. Both solvent extraction and spectroscopic studies established that this cavity shows the high selectivity toward Cs+ among alkali metal cations, the high affinity with Ag+, and the moderate affinity with RNH3+. Very surprisingly, the association-dissociation processes for 2 and cesium picrate was so slow that the rate could be followed by a conventional spectroscopic method. The thermodynamic parameters determined by kinetic studies disclosed that the major driving-force for Cs+ inclusion is the entropy term based on the desolvation.

Kinetically stable complexes of alkali cations with calixspherands: An evaluation of shielding

Three new calixspherands (2-4) were synthesized in good yields (>60%) via a new method; p-tert-butylcalix-[4]arene (6) is bridged with a m-terphenyl (7-9) and subsequently alkylated. 1H NMR spectroscopy and X-ray crystallography showed that all the complexes are in a partial cone conformation. All the calixspherands form kinetically stable complexes with Na+, K+, and Rb+. The kinetic stability was determined both by 1H NMR spectroscopy, in CDCl3 saturated with D2O, and by a new method based on the exchange of radioactive rubidium or sodium in the complexes for nonradioactive sodium in different solvents. Both methods showed that the kinetic stability of the different complexes is strongly increased when the size of the group on the central aromatic ring of the m-terphenyl is increased. This effect is most pronounced for the rubidium complexes. The half-life times for decomplexation, in CDCl3 saturated with D2O, increased from 2.8 h for [1·Rb]+ to 139 h and 180 days for [2·Rb]+ and [3·Rb]+, respectively. The 'exchange method' shows that the rate of decomplexation is the rate-limiting step in the exchange of rubidium in the complex for sodium present in solution. These results can be explained in terms of increased shielding of the cavity from solvent molecules. The kinetic stabilities of the complex of 3 with Na+, K+, and Rb+ are the highest ever reported.

Kinetically Stable Complexes of Alkali Cations with Rigidified Calixarenes: Synthesis, X-ray Structures, and Complexation of Calixcrowns and Calixspherands

Selective 1,3-dialkylation of the phenolic groups of p-tert-butylcalixarene (3) with methyl or benzyl tosylate yields 7a (75percent) and 8 (95percent), respectively.Subsequent bridging of the two remaining phenolic groups in 7a or 8, by reaction with polyethylene glycol ditosylates, gives p-tert-butylcalixarene crown ethers (4b, 4c, and 4e).Reaction of 7a with 3,3''-bis(bromomethyl)-2,2',2''-trimethoxy-5,5',5''-trimethyl-1,1':3',1''-terphenyl (10) in the presence of NaH or KH produces the corresponding NaBr and KBr complexes of the calixspherand 6.Decomplexation of the6*NaBr and 6*KBr complexes in H2O/CH3OH (4:1) requires long reaction times and high temperatures, indicating a high kinetic stability.The X-ray structure of 6*NaPic confirmed the flattened partial cone conformation of the calixarene moiety in this complex.The free energies of complexation (ΔG0) of the calixcrown ether alkali picrate (MPic) complexes vary from -6 to -12 kcal*mol-1 (CDCl3).The calixspherand 6 forms kinetically "stable" complexes with Na(1+) (kd298 = 6.0*1E-9 s-1), K(1+) (kd298 =1.0*1E-8 s-1), and Rb(1+) (kd298 = 6.9*1E-5 s-1).The rates of complexation vary between 1.3*1E4 and 2.5*1E5 M-1 s-1.The calculated free energies of complexation of 6 with MPic salts in CDCl3 at 298 K are -16.8 , -18.1 , and -13.0 kcal*mol-1, respectively.The high thermodynamic and kinetic stabilities of these complexes are explained in terms of a high degree of preorganization of the calixspherand and the highly hydrophobic collar around the molecular cavity.This prevents solvent molecules to assist in the decomplexation process.

Crown Ethers of Low Symmetry. Spiro Crown Ethers and 16-Crown-5 Derivatives

Spiro crown ethers 3a-c, spiro bis(crown ethers) 5a-e, and the related 16-crown-5 derivatives 6a-d were synthesized and their cation binding abilities were evaluated by study of the extraction of aqueous alkali picrates.Crown ethers carrying 13-crown-4 and 16-crown-5 skeletons showed significant changes in cation selectivity as compared with the corresponding 12-crown-4 and 15-crown-5.Spiro-13-crown-4 3a and spiro-bis 5a showed extremely low extractabilities for all cations examined, while the 16-crown-5-derivatives, including spiro-bis 5b and spiro-bis 5c, showed anomalously high Na+ selectivity.In a quantitative study of extraction equilibrium constants (Kex), 16-crown-5 was again found to have much higher selectivity for Na+ than 15-crown-5.This result is attributed to the less symmetrical spatial arrangement of donor oxygen atoms in 16-crown-5; the symmetry-extractability relationship is discussed on the basis of the size-fit concept.