Structural studies on encapsulation of tetrahedral and octahedral anions by a protonated octaaminocryptand cage.

Structural aspects of the binding of inorganic anions such as perchlorate, hydrogen sulfate, and hexafluorosilicate with the proton cage of octaaminocryptand L(1), N(CH(2)CH(2)NHCH(2)-p-xylyl-CH(2)NHCH(2)CH(2))(3)N), are examined thoroughly. Crystallographic results for a hexaprotonated perchlorate complex of L(1), [(H(6)L(1))(6+)(ClO(4) (-))]5(ClO(4) (-)).11H(2)O.CH(3)CN (1), an octaprotonated hydrogen sulfate complex of L(1), [(H(8)L(1))(8+)(HSO(4) (-))]7(HSO(4) (-)).3H(2)O.CH(3)OH (2) and an octaprotonated fluorosilicate complex of L(1), [(H(8)L(1))(8+)(HSiF(6) (-))]3(SiF(6) (2-)).(HSiF(6) (-)).15H(2)O (3), show encapsulation of one perchlorate, hydrogen sulfate and hexafluorosilicate, respectively inside the cage of L(1) in their protonated states. Further, detailed structural analysis on complex 1 reveals that the hexaprotonated L(1) encapsulates a perchlorate via two N-H...O and five O-H...O hydrogen bonds from protonated secondary nitrogen atoms of L(1) and lattice water molecules, respectively. Encapsulated hydrogen sulfate in complex 2 is "glued" inside the octaprotonated cage of L(1)via four N-H...O and six C-H...O hydrogen bonds whereas encapsulated HSiF(6) (-) in complex 3 has short contacts via six N-H...F and three C-H...F hydrogen bonds with [H(8)L(1)](8+). In the cases of complexes 2 and 3, the cryptand L(1) in octaprotonated state shows monotopic encapsulation of the guest and the final conformation of these receptors is spherical in nature compared to the elongated shape of hexaprotonated state of L(1) in complex 1.

Spherical versus linear anion encapsulation in the cavity of a protonated azacryptand.

Grams scale synthesis of an octaaminocryptand L(2) with high yield is obtained in one-pot by low-temperature [2 + 3] condensation of tris(2-aminoethyl)amine with isophthalaldehyde, followed by sodium borohydride reduction. Structural aspects of octaaminocryptand L(2) x MeOH, binding of iodide (spherical) and bichloride (linear) in L(2), (1,4,11,14,17,24,29,36-octa-azapentacyclo-[12.12.12..2(6,9).2(19,22).2(31,34)]-tetratetraconta 6(43),7,9(44),19(41),20,22(42),31(39),32,34(40)-nonane, N(CH2CH2NHCH2-m-xylyl-CH2NHCH2CH2)3N), in the hexaprotonated and tetraprotonated states, respectively, are examined. Crystallographic results show binding of single iodide [H6L(2)I](I)5 x 4 H2O, (2), in a hexaprotonated cryptand L(2). Monotopic recognition of iodide is observed via (N-H)(+)...iodide interactions. The tetraprotonation of L(2) by hydrochloric acid showed the formation and encapsulation of a bichloride inside the cavity, which is examined from the single-crystal X-ray study. Encapsulation and binding of a proton-bridged linear bichloride inside the cavity of tetraprotonated L(2), [H4L(2)(ClHCl)](Cl)3 x nH2O (3), via (N-H)(+)...chloride interactions is observed in the structural investigation. This study shows that degree of protonation and its distribution in the receptor architecture play an important role in guest encapsulation. Further, it represents the first example of an encapsulated bichloride inside the cavity of an organic host.

Trapped inorganic phosphate dimer.

Single crystal X-ray crystallographic signature of the pentafluorophenyl substituted tripodal urea-based receptor shows formation of a pseudo dimeric cage which also encapsulates a phosphate dimer via numerous hydrogen bonding and anion[dot dot dot]pi interactions.

Body proportions in Fanconi anemia heterozygotes.

To study the anthropometric ratios in parents (heterozygotes) of children with Fanconi anemia. The study was carried out in the Department of Hematology, Institute of Child Health & Hospital for Children, Chennai. Parents of children with Fanconi anemia were the subjects of the study. Applying standard instruments and methods, various body measurements were recorded. 31 fathers and 37 mothers were included in the study. A hundred male and female controls of the same ethnic group were also studied for the same parameters. The ratios were calculated and statistically analyzed. It was observed that fathers (male heterozygotes) had shorter forearms, the ratio of upper arm: forearm was significantly increased compared to male controls. In mothers (female heterozygotes) the inter-pupillary distance was increased, the ratio of head circumference to inter-pupillary distance was decreased compared to female controls.

Pregnancy-exaggerated galactosemia and congenital cataracts.

One child in a family and two children in another family had galactosemia and congenital cataract. Two of them had total soft cataracts while in one, cataract was less soft. In addition, they had mild lactosuria. The mothers of the affected children had significant lactosuria and mild galactosuria without cataracts. Fathers did not have galactosuria or lactosuria. Clinically unaffected siblings in one family had mild galactosuria and lactosuria. Pregnancy-exaggerated galactosemia was suspected in these two mothers who gave birth to children with congenital cataract. As an extension of this work, 5001 pregnant women were screened for galactose in urine just before the delivery of babies. Mild galactosuria was present in 54 (1.08%). Three children had congenital cataract and one had changes in posterior pole and cornea. Restriction of lactose by reducing intake of milk and milk products during pregnancy by mothers with galactosuria is recommended to avoid the birth of children with congenital cataract.

A rare case of ectopic thoracic kidney and spleen.

A 23-year-old male presented with fever of 5 days duration. His peripheral smear was positive for Plasmodium vivax. He was treated for malaria and responded. During investigation with USG it was found that he had absent left kidney. An abdominal contrast enhanced CT scan revealed ectopic kidney and spleen in the left hemithorax. This was a rare case of ectopic thoracic kidney and spleen.

Molecular Self Assembly: Solvent Guests Tune the Conformation of a Series of 2,6-Bis(2-anilinoethynyl)pyridine-Based Ureas.

The conformations of 2,6-bis(2-anilinoethynyl)pyridine-based urea receptors were studied by single crystal X-ray diffraction methods and revealed a rich conformational flexibility influenced by solvents. Whereas receptor L(1) in DMSO prefers an "S" conformation, receptor L(1) crystallizes in an "O" conformation from DMSO/CH(3)OH binary solvent system, and a "W" conformation in the ternary solvent mixture DMSO/toluene/1,4-dioxane. In the case of L(2), the molecule adopts an "S" conformation where water molecules are sandwiched between two molecules of L(2) to form a dimer. Similar to L(2), L(3) also forms a dimer where water molecules are sandwiched between L(3) molecules, which are capped with two molecules of DMSO. Such a capping DMSO solvate is lacking in the case of L(2). Taken together, these results demonstrate that the conformation of 2,6-bis(2-anilinoethynyl) pyridine-based urea receptors can be dramatically manipulated and tuned by the choice of crystallization solvents.

Anion complexation of a pentafluorophenyl-substituted tripodal urea receptor in solution and the solid state: selectivity toward phosphate.

The binding and selectivity of halides (spherical) and oxyanions (tetrahedral) toward a recently reported pentafluorophenyl-substituted tripodal urea-based receptor L(1) are examined thoroughly in the solid state by single-crystal X-ray crystallography as well as in solution by multinuclear NMR techniques. Crystallographic results show proof of a fluoride encapsulation in the cavity of L(1) in complex [L(1)(F)][Bu(4)N], . Fluoride encapsulation inside the C(3v) symmetric cleft is observed via six hydrogen bonds to all six urea protons of the receptor. In case of complex crystallographic results show encapsulation of sulfate ion inside a supramolecular cage formed upon 1 : 2 (guest-host) complex formation between sulfate and L(1). Sulfate encapsulation is observed via fourteen hydrogen bonding interactions from all six urea moieties of two L(1) units. Our effort to isolate single crystal of halides/oxyanions complexes of L(2) always yield single crystals of free L(2) though literature shows anion binding with this receptor in solution. Solution state binding studies of L(1) are carried out by (1)H-NMR titration to calculate binding constants, which show the following anion binding sequence H(2)PO(4)(-) > SO(4)(2-)> CH(3)COO(-) > F(-) > Cl(-) >> Br(-) whereas there is no binding with I(-), NO(3)(-) and ClO(4)(-) guests. Comparison of phosphate and sulfate binding in L(1) and L(2), show higher binding with the pentafluorophenyl substituted receptor, L(1). Further (19)F and (31)P-NMR experiments in solution are also carried out to probe the binding of F(-) and H(2)PO(4)(-) with L(1), respectively. Extensive (1)H-NMR experiments in solution and crystallization in the presence of multiple anions are also undertaken to evaluate the selectivity of H(2)PO(4)(-) over other anions.

Encapsulation of halides within the cavity of a pentafluorophenyl-substituted tripodal amine receptor.

Pentafluorophenyl-substituted tripodal amine L, tris[[(2,3,4,5,6-pentafluorobenzyl)amino]ethyl]amine, is becoming a potential receptor for encapsulation of Cl- and Br- within the pseudo-C3-symmetric tris(2-aminoethyl)amine (L1) cavity upon protonation of the secondary amines. 1H NMR titration results indicate that [H3L]3+ binds with Cl- and Br- strongly compared to the [H3L2]3+ receptor, where L2 is N,N',N' '-tris[(2-benzylamino)ethyl]amine.

Synthesis and characterization of a tripodal amide ligand and its binding with anions of different dimensionality.

Synthesis and crystal structure of a tren-based amide, L(1), N,N',N''-tris[(2-amino-ethyl)-3-nitro-benzamide] is reported. The crystallographic results show intramolecular hydrogen bonding and aromatic pi...pi stacking among tripodal arms which prevent opening of the receptor cavity. Intermolecular hydrogen bonding in L1 generates the sheetlike network in the solid state. The structural aspects of binding halides (1 and 2), nitrate (3), perchlorate (4), and hexafluorosilicate (5) with the protonated L1 are examined crystallographically. Protonation at the apical nitrogen of L1 in the presence of anions shows a structural transformation from sheet to bilayer network. Anion binding with multiple receptor units is observed via amide N-H...anion and aryl C-H...anion hydrogen-bonding interactions in all the complexes. The aryl group having nitro functionality that contributes to anion binding in complexes 1-5 through CH...anion interactions (either para or meta to nitro C-H) is noteworthy. These studies also show higher anion coordination of chloride (8) and hexafluorosilicate (14) with L1H+.

Solid state structural evidence of chloroform-benzene-chloroform adduct trapped in hexaanthryl octaaminocryptand channels.

Structural aspects governing the formation and stabilization of adducts in the organic channels were examined. An unprecedented structural evidence of an inverted sandwich-type benzene/chloroform (1:2) adduct was isolated within the channel formed by close packing of an aromatic substituted aminocryptand 1 host. Interestingly, this adduct was stabilized through several short contacts with the channel wall. Crystallographic study further showed that a channel formed by self-assembly of 1 can also encapsulate chloroform as a guest. Thermal analysis confirms that the chloroform-benzene-chloroform adduct as a guest has better thermal stability than that of the chloroform guest within the channel.

Formation of an infinite 2D-layered water of (H2O)45 cluster in a cryptand-water supramolecular complex: a template effect.

Structural aspects governing the formation of the water layer in the octaaminocryptand L were examined. Crystallographic results reveal an unprecedented, infinite two-dimensional (2D) layer of water molecules by interconnection of (H2O)45 clusters under confined conditions. This unique 2D layer is basically a template effect of L where the N4 donor sets facilitate the formation of the crown shape water at both ends which, on propagation, generates an infinite through-channel down the c-axis. Thermal analysis, powder X-ray diffraction, and IR studies carried out on L.(H2O)15, 1, support the crystallographic results.

Counteranion-controlled water cluster recognition in a protonated octaamino cryptand.

Structural aspects of binding of water cluster and halides in the octaamino cryptand L (1,4,11,14,17,24,29,36-octaazapentacyclo[12.12.12.2.(6,9)2.(19,22)2(31,34)]tetratetraconta-6(43),7,9(44),19(41),20,22(42),31(39),32,34(40)-nonaene, N(CH2CH2NHCH2-p-xylyl-CH2NHCH2CH2)3N) in a protonated state were examined. Crystallographic results show binding of the acyclic quasiplanar water tetramer [H4L(H2O)4](I)4.2.57H2O (1) in a tetraprotonated cryptand L having an iodide counteranion, where two water molecules reside inside the two tren-based cavity, bridged by a third water molecule, and a fourth external water molecule is hydrogen bonded to the bridged water molecule. In the case of complexes [H6L(Br)][(Br)6H].4H2O.2HBr (2) and [H6L(Cl)][(Cl)6H].10.86H2O (3), a single bromide and chloride occupied, respectively, the inside of the cryptand cavity, where L is in a hexaprotonated state. Monotopic recognition of bromide/chloride was observed at the center of the cryptand cavity where halides show C-H...halide interactions instead of the N-H...halide interactions reported in the ditopic complexes of halides with the same cryptand, 5 and 6. Thermal analyses on 1-3 were carried out, and the data obtained distinctly differentiate water cluster complex 1 from the anion-encapsulated cryptates 2 and 3. This study represents the first example of anion-controlled cluster formation inside the cavity of a cryptand.