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Heteroditopic Cryptands of Tunable Cavity Size: Imposition of Distorted Geometry onto Copper(II) and Nickel(II) and Molecular Recognition of Water Molecules
, Bharadwaj P.K.
Published in American Chemical Society
Volume: 37
Issue: 20
Pages: 5050 - 5055
Complexation behavior of a previously described heteroditopic cryptand L1 and a newly synthesized cryptand L2 toward transition metal ions is described. The cryptands readily accept a transition metal ion like Cu(II) or Ni(II) at the N4 end of the cavity forming mononuclear cryptates. The Cu(II)-cryptate of L1 further accepts a water molecule to form [Cu(L1(OH2)]̇(picrate)2(H2O), i.e.. C45H53N11O19Cu. This molecule crystallizes in the monoclinic space group C2/c with a = 34.199(8) Å, b = 12.286(5) Å, c = 23.289(7) Å, β= 93.12(4)°, Z = 8. The O atom of the water molecule is strongly bonded to the Cu(II) ion. while its H atoms are H-bonded to the nearest benzene rings. The UV-vis spectral and magnetic studies of the complexes are consistent with the mononuclear nature of the cryptates. Cryptand U undergoes diprotonation upon treatment with a mineral acid like HCl or HClO4. This diprotonated cryptand is found to be a good host for two molecules of water inside the cavity. The diperehlorate salt. [H2L1C(H2O)1.5]̇(ClO 4)2̇(H2O)0.75, i.e.. C33H51.5Cl2N5O13.25, crystallizes in the monoclinic space group P21/c with a = 12.204(1) Å, c = 11.465(1) Å, c = 28.537(3) Å, β = 91.98(2)̊, Z = 4. The cryptand has an ellipsoidal cavity with both the bridgehead N atoms adopting an endo-endo conformation in the solid state. The water O atoms O(1w) and O(2w) lie in the pseudo 3-fold axis joining the two bridgehead N atoms. Occupancy of O(2w) is found to he 0.5 while that of O(1w) is unity. The water molecules are held inside the cavity through H-bonding with an ice-like structure. The FAB-mass spectral data and the bond distances involving the water oxygens suggest that both the water molecules are tightly held inside the cavity. The present cryptate is the first X-ray crystallographically characterized complex with two water molecules inside the cavity of a cryptand.
About the journal
JournalData powered by TypesetInorganic Chemistry
PublisherData powered by TypesetAmerican Chemical Society
Open AccessNo