Coordination Chemistry of Acrylamide 4. Crystal Structures and IR Spectroscopic Properties of Acrylamide Complexes with CoII,NiII, and ZnII nitrates

Acrylamide complexes of metal nitrates: [M(O‐OC(NH₂)CHCH₂)_n(H₂O)_m][NO₃]₂ (M = Co( 1 ), Ni( 2 ) (n = 6 and m = 0) and Zn( 3 ) (n = 4 and m = 2)) have been determined by using single crystal X‐ray diffraction analysis. All complexes crystallize in the triclinic space group . The structures of 1 and 2 represent octahedral species [M(AAm)₆]²⁺ (AAm = O‐OC(NH₂)CHCH₂ and M = Co or Ni) and uncoordinated nitrate ions. The structure of 3 involves the octahedral cation [Zn(AAm)₄(H₂O)₂]²⁺ in which the Zn²⁺ environment includes oxygen atoms of four acrylamide and two water molecules that are stabilized using ionic nitrate ions. The observations of the solid‐state IR spectroscopic vibrational frequencies of these acrylamide complexes are in agreement with the crystal structures.     

Compensation of steric demand by cation-pi interactions,cobaltocenium cations as guests in tetraurea calix[4]arene dimers

The affinities of ferrocene (2) and the cobaltocenium cation (3+), which have roughly the same size and differ in their charge, towards the inner cavity of the dimeric capsule formed by tetraurea calix[4]arene (1) were studied in C2D4Cl2 solutions. While 3+, which occupies more than 75% of the internal volume of the dimer, is readily encapsulated this is not the case for 2. This is probably due to cation-pi interactions, which operate only between 3+ and the aromatic rings of the calix[4]arene dimer. We found that the affinity of the cobaltocenium cation is higher than that of the tropylium cation (4+) and is only 2-3 times less than that of the tetraethylammoniun cation (5+). From the variable temperature 1H NMR spectra of this capsule, the free energy of activation at 298 K (deltaGdouble dagger(298K)) for the reorientation of the hydrogen bonded belt between the two parts of the dimer could be determined by total line shape analysis for the aromatic protons of the calixarene. The value of 14.3 +/- 0.2 kcal mol(-1) for the dimeric capsules of 3+ PF6- is very similar to the free activation energy found for dimeric capsules of 1 with 4+ PF6- and 5+ PF6- in C2D4Cl2. It becomes significantly lower, if PF6- is replaced by BF4-. We also found that ten times more DMSO is needed to disrupt the capsule 1 x 3+ x 1 than the corresponding 1 x 1 dimer containing benzene as guest. This demonstrates again the importance of the cation-pi interactions for the stability of such hydrogen-bonded dimeric capsules.     

Synthesis and Crystal Structure of [C10N2H10]2[P2Mo5O21(OH)2]·2H2O

The crystal structure of [C₁₀N₂H₁₀]₂[P₂Mo₅O₂₁(OH)₂] · 2H₂O, contains the heteropolyanion, [P₂Mo₅O₂₁(OH)₂]^4—, together with diprotonated 4, 4′‐bipyridine. The heteropolyanion is built up from five MoO₆ octahedra sharing four common edges and one common corner, capped by two PO₃(OH) tetrahedra. The structure is stabilized by hydrogen bonds involving the hydrogen atoms of the 4, 4′‐bipyridine, water molecules and the oxygen atoms of the pentamolybdatobisphosphate. This is the first example that this kind of cluster could be isolated in the presence of a poly‐functional aromatic molecule ion. Crystal data: triclinic, P1¯ (No. 2), a = 9.983(2)Å, b = 11.269(2)Å, c = 17.604(4)Å, α = 73.50(3)°, β = 84.07(3)°, γ = 67.96(3)°; V = 1760.0(6)ų; Z = 2; R₁ = 0.037 and wR₂ = 0.081, for 9138 reflections [I > 2σ(I)].     

Self-assembly of tetrahedral and trigonal antiprismatic clusters [Fe4(L4)4] and [Fe6(L5)6] on the basis of trigonal tris-bidentate chelators

In a one-pot reaction, the tetranuclear iron chelate complex [Fe4(L4)4] 6 was generated from benzene-1,3,5-tricarboxylic acid trichloride (4), bis-tert-butyl malonate (5a), methyllithium, and iron(II) dichloride under aerobic conditions. Alternatively, hexanuclear iron chelate complex [Fe(L5)6] 7 was formed starting from bis-para-tolyl malonate (5b) by employing identical reaction conditions to those applied for the synthesis of 6. The clusters 6 and 7 are present as racemic mixtures of homoconfigurational (delta,delta,delta,delta)/(lambda,lambda,lambda,lambda)-fac or (delta,delta,delta,delta,delta,delta)/(lambda,lambda,lambda,lambda,lambda,lambda)-fac stereoisomers. The structures of 6 and 7 were unequivocally resolved by single-crystal X-ray analyses. The all-iron(III) character of 6 and 7 was determined by M?ssbauer spectroscopy.     

Structural Patterns and Dimensionality in Magnesium Borophosphates: The Crystal Structures of Mg2(H2O)[BP3O9(OH)4] and Mg(H2O)2[B2P2O8(OH)2]·H2O

Hydrothermal investigations in the system MgO/B₂O₃/P₂O₅(/H₂O) yielded two new magnesium borophosphates, Mg₂(H₂O)[BP₃O₉(OH)₄] and Mg(H₂O)₂[B₂P₂O₈(OH)₂]·H₂O. The crystal structures were solved by means of single crystal X‐ray diffraction. While the acentric crystal structure of Mg₂(H₂O)[BP₃O₉(OH)₄] (orthorhombic, P2₁2₁2₁ (No. 19), a = 709.44(5) pm, b = 859.70(4) pm, c = 1635.1(1) pm, V = 997.3(3) × 10⁶ pm³, Z = 4) contains 1D infinite chains of magnesium coordination octahedra interconnected by a borophosphate tetramer, Mg(H₂O)₂[B₂P₂O₈(OH)₂]·H₂O (monoclinic, P2₁/c (No. 14), a = 776.04(5) pm, b = 1464.26(9) pm, c = 824.10(4) pm, β = 90.25(1)°, V = 936.44(9) × 10⁶ pm³,Z = 4) represents the first layered borophosphate with 6³ net topology. The structures are discussed and classified in terms of structural systematics.     

Topochemical Reactions in Langmuir-Blodgett Multilayers

Abstract

The topochemical polymerization of diacetylenes and.the dimerization of cinnamic acid derivatives have been studied in Langmuir-Blodgett-multilayers. The resulting polymer films are of controlled thickness and morphology and exhibit excellent stability. Structure, morphology and phase changes occuring in monomer and polymer films have been investigated using spectroscopic methods, electron and x-ray diffraction. Possible applications of the polymer films are discussed.