Spontaneous formation of novel luminescent dinuclear lanthanide complexes that emit in the visible and near-IR regions.

The reaction of tetrasodium-4,4',6,6'-tetracarboxy-2,2'-bipyridine (Na(4)L) with various lanthanide ions yields a family of isostructural supramolecular {Na(2)[Ln(2)L(2)]} complexes (1-4), where Ln(III) = Eu, Nd, Gd, and Tb. Strikingly, these complexes luminesce in buffered H(2)O or D(2)O solutions in either the visible or near-IR regions, despite their high hydration states.

A new twist in anion binding: metallo-helicate hosts for anionic guests.

The condensation of 5-chlorocarbonyl-2,2'-bipyridine with a variety of rigid aromatic diamines, L, gave a series of new bisamido-2,2'-bipyridine based ligands (L = 4,4'-methylenediamine, L1; L = 1,1-bis(4-aminophenyl)cyclohexane, L2; L = 1,1-bis(4-amino-3,5-dimethylphenyl)cyclohexane, L3) capable of forming dinuclear triple helicate complexes on coordination to Fe(II). The reaction of various Fe(II) salts with gave: {[Fe2(L1)3](BF4)4, 1; [Fe2(L1)3](ClO4)4, 2; [Fe2(L1)3]Cl4, 3; [Fe2(L1)3](SO4)2, 4; [Fe2(L2)3](BF4)4, 5; [Fe2(L2)3]Cl4, 6; [Fe2(L3)3](BF4)4; 7; [Fe2(L3)3]Cl4, 8; and [Fe2(L3)3](SO4)2, 9, as determined by UV-Vis, IR and 1H NMR spectroscopy, electrospray mass spectrometry (ESMS) and elemental analyses. A UV-Vis complexometric titration experiment between L3 and Fe(BF4)2 established conclusively a [Fe2(L3)3]4+ product species. 1H NMR spectroscopy showed that the complexes exist as both rac-(helical) and meso-(non-helical) isomers in DMSO-d6 solution at 298 K. L1-L3 were designed such that following complexation, six amide hydrogen atoms would line an inter-strand intrahelical cavity of sufficient size to facilitate the binding of guest species within it. Indeed, ESMS studies showed characteristic peaks typical of complex-anion species in solution. Furthermore, 1H NMR titration experiments showed that anions bind within the intrahelical cavity as titration of 1, 5 and 7 with Bu4NCl showed significant downfield shifts in the amide and bipyridyl H6 proton resonances to yield a species of 1 : 2 host to guest stoichiometry. Moreover, addition of Bu4NCl to 1, 5 and 7 shifted the rac-/meso-species distribution from 1 : 2 in favour of the meso- to 100% in favour of the rac-isomer, showing that Cl- ions favour the formation of the triple helicate species in DMSO-d6 solution.

Dinuclear complexes of a pseudocalixarene macrocycle: structural consequences of intramolecular hydrogen bonding.

A series of dinuclear complexes of a pseudocalixarene macrocycle H6L containing two 2,2'-methylenediphenol groups have been synthesised and structurally characterised. Using divalent metal ions, complexes containing a common hyperbolic paraboloid (saddle) M2(H4L)2+ core are formed. The structure is controlled by two strong O-H-O interactions resulting from metal ion-promoted monodeprotonation of the methylenediphenol units. The metal ions are located in a cleft within which neutral or anionic guests can bind. Use of trivalent metal ions leads to complete deprotonation of the phenol groups and loss of the saddle conformation.

Trigonal bipyramidal geometry and tridentate coordination mode of the tripod in FeCl(2) complexes with tris(2-pyridylmethyl)amine derivatives bis-alpha-substituted with bulky groups. structures and spectroscopic comparative studies.

A series of dichloroferrous complexes with ligands derived from the tris(2-pyridylmethyl)amine tripod has been prepared and characterized. The X-ray crystal structures of the complexes [bis(2-bromo-6-pyridylmethyl)(2-pyridylmethyl)amine]Fe(II)Cl(2) ((Br(2)TPA)Fe(II)Cl(2)) and [bis(2-phenyl-6-pyridylmethyl)(2-pyridylmethyl)amine]Fe(II)Cl(2), ((Ph(2)TPA)Fe(II)Cl(2)) are reported. In these complexes, the tripod coordinates in the tridentate mode, with a substituted pyridyl arm dangling away from the metal. Both complexes have a trigonal bipyramidal iron center with two equatorial chloride ions. Their crystal structures are compared with those of the [tris(2-pyridylmethyl)amine]Fe(II)Cl(2) and [(2-bromo-6-pyridylmethyl)bis(2-pyridylmethyl)amine]Fe(II)Cl(2) complexes ((TPA)Fe(II)Cl(2) and (BrTPA)Fe(II)Cl(2), respectively) in which the ligand coordinates in the tetradentate mode. For all complexes, the metal to ligand distances are systematically above the value of 2.0 A, and (1)H NMR displays paramagnetically shifted resonances with short relaxation times. This indicates that the iron is in a high-spin state. Electric conductivity measurements show that, for all complexes, the measured values lie within the same range, significantly below those expected for ionic complexes. Together with the analysis of the UV-visible and NMR data, this strongly suggests that the coordination mode of the tripod is retained in solution.

5,5'-Di-tert-butyl-2,2'-dihydroxy-3,3'-methanediyldibenzaldehyde and its allyl-protected dialcohol and dialdehyde precursors.

5,5'-Di-tert-butyl-2,2'-dihydroxy-3,3'-methanediyldibenzaldehyde, C(23)H(28)O(4), (IV), has been structurally characterized in two polymorphic forms. The tetragonal form, (in I4(1)/a) has been reported previously but is redetermined and reinterpreted here, while the monoclinic form, (in C2/c) is reported for the first time. In both polymorphs, the molecule lies on a crystallographic twofold axis. Two precursors in the synthesis of (IV), namely 2,2'-bis(allyloxy)-5,5'-di-tert-butyl-3,3'-methanediyldibenzenemethanol (C(29)H(40)O(4)) and 2,2'-bis(allyloxy)-5,5'-di-tert-butyl-3,3'-methanediyldibenzaldehyde (C(29)H(36)O(4)) have also been characterized.