Copper phthalate coordination polymers incorporating kinked dipyridyl ligands: an unprecedented 8-connected network and one-dimensional chiral nanobarrels with hydrophobic channels constructed from septuple helical motifs.

Copper phthalate coordination polymers incorporating the kinked and hydrogen-bonding-capable imines 4,4'-dipyridylketone (dpk) and 4,4'-dipyridylamine (dpa) have been prepared and structurally characterized by single-crystal X-ray diffraction. {[Cu(pht)(dpk)].0.33CH(3)OH}(n) (1; pht = phthalate) possesses helical subunits built from the fusion of [Cu(dpk)](n) 3-fold double helices and [Cu(pht)](n) 3-fold helices with opposite handedness. The resulting achiral [Cu(pht)(dpk)](n) helices are conjoined by bridging phthalate carboxylate oxygen atoms to construct {Cu(2)O(2)} dimeric units, which serve as 8-connected nodes for a three-dimensional (3D) coordination polymer lattice with an unprecedented 3(6)4(12)5(8)6(2) topology, evocative of a 3D Kagome lattice. {[Cu(2)(pht)(2)(dpa)].H(2)O}(n) (2) manifests homochiral septuple left-handed [Cu(2)O(2)(dpa)](n) helices formed by copper ions, phthalate oxygen atoms, and dpa ligands. The septuple helices are bracketed by pht anions to construct chiral one-dimensional nanobarrels with solvent-free "star-shaped" channels. Compounds 1 and 2 display antiferromagnetic [J = -9.85(5) cm(-1)] and ferromagnetic [J = +1.36(3) cm(-1)] coupling across their {Cu(2)O(2)} dimeric units, respectively.

A chiral luminescent coordination polymer featuring a unique 4-connected self-catenated topology built from helical motifs.

The luminescent chiral coordination polymer {[Cd(pht)(dpa)(H(2)O)] x 4 H(2)O}(n) (pht = phthalate; dpa = 4,4'-dipyridylamine) possesses an unprecedented 4-connected uninodal self-catenated three-dimensional 7(4)8(2) network topology, constructed from the interlocking of [Cd(dpa)](n) double helices with [Cd(pht)](n) single helices.

Cadmium dicarboxylate coordination polymers incorporating a long-spanning organodiimine: in situ alkene isomerization and an unprecedented chiral 6(5)8 two-dimensional network.

Reaction of cadmium nitrate, maleic acid, and N,N'-bis(4-pyridylmethyl)piperazine (bpmp) in a methanol/water mixed solvent system at 25 degrees C resulted in an unexpected in situ isomerization and formation of [[Cd(fumarate)(bpmp)(H2O)2] x 2H2O]n (1), which exhibits a system of mutually interpenetrated [Cd(fumarate)(bpmp)(H(2)O)]n grid-like coordination polymer layers. A similar reaction using cadmium chloride and succinic acid produced [[Cd(succinate)(bpmp)(CH3OH)] x 2H2O]n (2), which manifests a chiral two-dimensional coordination polymer network with an unprecedented 6(5)8 topology. The differences in the conformations of the four-carbon dicarboxylate tethers (anti in , gauche in ) and cadmium coordination environment (octahedral in , pentagonal bipyramidal in ) play a significant role in structure direction during self-assembly. Thermal properties of and are also reported.

Self-catenated and interdigitated layered coordination polymers constructed from kinked dicarboxylate and organodiimine ligands.

Hydrothermal combination of divalent nickel or cobalt nitrates with the kinked carboxylic acid 4,4'-oxybis(benzoic acid) (H2oba) and the kinked and hydrogen-bonding capable organodiimine 4,4'-dipyridylamine (dpa) under basic conditions has afforded a pair of coordination polymers with a formulation of {[M(oba)(dpa)] x H2O} (M = Ni, 1; M = Co, 2). Both materials were characterized by single-crystal X-ray diffraction, infrared spectroscopy, and thermogravimetric analysis. The structures of 1 and 2 are isomorphous and manifest intriguing self-catenated two-dimensional layered motifs with very rare non-diamond 66 topology constructed from the direct covalent linkage of [M(oba)]n double helices through [M(dpa)]n undulating chains. Adjacent self-catenated layers engage in mutual interdigitation to form double-layer patterns that further aggregate via supramolecular hydrogen-bonding patterns imparted by the central amine of the dpa ligand. These coordination polymers are very thermally robust, with decomposition occurring only above 400 degrees C.

Diverse entangled metal-organic framework materials incorporating kinked organodiimine and flexible aliphatic dicarboxylate ligands: synthesis, structure, physical properties, and reversible structural reorganization.

Hydrothermal synthesis has afforded a family of divalent metal adipate (adp) coordination polymers incorporating the kinked dipodal organodiimine 4,4'-dipyridylamine (dpa). As revealed by single-crystal X-ray diffraction, the structures of these materials are critically dependent on the metal coordination geometry, the carboxylate binding modes, and the conformations of the flexible adipate moieties. In all cases, hydrogen-bonding interactions imparted by the dpa tethers also play a structure-directing role. All materials were further characterized via infrared spectroscopy and elemental and thermogravimetric analysis. [Co(adp)(dpa)] (1) displays doubly interpenetrated three-dimensional (3-D) networks with a decorated alpha-Po-type (pcu) topology. In contrast, [Ni(adp)(dpa)(H2O)] (2) possesses a triply interpenetrated binodal cooperite-type (pts) framework, the highest level of interpenetration yet reported for this structure type. [Zn(adp)(dpa)].H2O (3) presents mutually inclined polycatenated 2-D graphitic layers consisting of neutral dimeric [Zn2(mu2-adp)2] kernels conjoined by dipodal dpa ligands. Compound 1 exhibited weak antiferromagnetic coupling between its carboxylate-bridged Co atoms, following Curie-Weiss behavior with Theta=-3.3 K. Compound 3 manifested blue light emission under ultraviolet excitation, as well as a reversible structural reorganization upon dehydration/rehydration.

The interaction of MS-325 with human serum albumin and its effect on proton relaxation rates.

MS-325 is a novel blood pool contrast agent for magnetic resonance imaging currently undergoing clinical trials to assess blockage in arteries. MS-325 functions by binding to human serum albumin (HSA) in plasma. Binding to HSA serves to prolong plasma half-life, retain the agent in the blood pool, and increase the relaxation rate of water protons in plasma. Ultrafiltration studies with a 5 kDa molecular weight cutoff filter show that MS-325 binds to HSA with stepwise stoichiometric affinity constants (mM(-1)) of K(a1) = 11.0 +/- 2.7, K(a2) = 0.84 +/- 0.16, K(a3) = 0.26 +/- 0.14, and K(a4) = 0.43 +/- 0.24. Under the conditions 0.1 mM MS-325, 4.5% HSA, pH 7.4 (phosphate-buffered saline), and 37 degrees C, 88 +/- 2% of MS-325 is bound to albumin. Fluorescent probe displacement studies show that MS-325 can displace dansyl sarcosine and dansyl-L-asparagine from HSA with inhibition constants (K(i)) of 85 +/- 3 microM and 1500 +/- 850 microM, respectively; however, MS-325 is unable to displace warfarin. These results suggest that MS-325 binds primarily to site II on HSA. The relaxivity of MS-325 when bound to HSA is shown to be site dependent. The Eu(III) analogue of MS-325 is shown to contain one inner-sphere water molecule in the presence and in the absence of HSA. The synthesis of an MS-325 analogue, 5, containing no inner-sphere water molecules is described. Compound 5 is used to estimate the contribution to relaxivity from the outer-sphere water molecules surrounding MS-325. The high relaxivity of MS-325 bound to HSA is primarily because of a 60-100-fold increase in the rotational correlation time of the molecule upon binding (tau(R) = 10.1 +/- 2.6 ns bound vs 115 ps free). Analysis of the nuclear magnetic relaxation dispersion (T(1) and T(2)) profiles also suggests a decrease in the electronic relaxation rate (1/T(1e) at 20 MHz = 2.0 x 10(8) s(-1) bound vs 1.1 x 10(9) s(-1) free) and an increase in the inner-sphere water residency time (tau(m) = 170 +/- 40 ns bound vs 69 +/- 20 ns free).

Displacement of Inner-Sphere Water Molecules from Eu(3+) Analogues of Gd(3+) MRI Contrast Agents by Carbonate and Phosphate Anions: Dissociation Constants from Luminescence Data in the Rapid-Exchange Limit.

Europium(III) (7)F(0) --> (5)D(0) excitation spectroscopy is used to determine if the anions carbonate and phosphate present in physiological fluids are able to displace water molecules from the first coordination sphere of Eu(3+) analogues of Gd(3+) MRI contrast agents. A lengthening of the Eu(3+) excited state lifetime in the presence of millimolar concentrations of carbonate or phosphate indicates that water molecules are displaced by an anion. Only those metal complexes that contain negatively charged ligands and more than one water molecule in the first coordination sphere of Eu(3+) have their water molecules displaced by saturating concentrations of carbonate or phosphate. Conditional dissociation constants, K(d)'s, for Eu(3+)-ligand complexes with phosphate or carbonate are determined from titrations wherein the Eu(3+) excited state lifetimes are monitored. For phosphate, K(d)'s lie in the range 1.2-90 mM, whereas for carbonate, the range is 35-200 mM. The titrations also indicate that only a single anion binds to a metal chelate complex and that the single anion may, under saturating anion concentrations, displace on average more than one, but not all, first coordination sphere water molecules. Eu(3+ 7)F(0) --> (5)D(0) excitation spectra indicate that, in some cases, many different Eu(3+)-containing species are in fast exchange in the presence of added anion, presumably involving different numbers of first coordination sphere water molecules. Our results show that, under physiological conditions, phosphate and carbonate will, on average, displace less than half of a water molecule from the first coordination sphere of a typical contrast agent and suggest that the effect on proton spin relaxation is likely to be minimal.