15 research outputs found
Oxotris(oxalate)niobate(V): An oxalate delivery agent in the design of building blocks
<p>This work concerns the oxalate delivery process that occurs when using (NH<sub>4</sub>)<sub>3</sub>[NbO(C<sub>2</sub>O<sub>4</sub>)<sub>3</sub>]Ā·6H<sub>2</sub>O as a suitable oxalate source in the synthesis of two compounds, [Cu(dmphen)(C<sub>2</sub>O<sub>4</sub>)(H<sub>2</sub>O)] (<b>1</b>) and [{Cu(dmphen)(CH<sub>3</sub>OH)}<sub>2</sub>(Ī¼-C<sub>2</sub>O<sub>4</sub>)](ClO<sub>4</sub>)<sub>2</sub> (<b>2</b>) (dmphenĀ =Ā 2,9-dimethyl-1,10-phenanthroline). {[Fe{HB(pz)<sub>3</sub>}(CN)<sub>2</sub>(Ī¼-CN)]<sub>2</sub>[{Cu(dmphen)}<sub>2</sub>(Ī¼-C<sub>2</sub>O<sub>4</sub>)]}ā<i>x</i>CH<sub>3</sub>OH (<b>3</b>) (2.0Ā ā¤Ā <i>x</i>Ā ā¤Ā 2.4) was obtained by reacting <b>2</b> and PPh<sub>4</sub>[Fe{HB(pz)<sub>3</sub>}(CN)<sub>3</sub>]āH<sub>2</sub>O [Ā =Ā tetraphenylphosphonium and Ā =Ā tris(pyrazolyl)borate]. Crystal structures of <b>1</b>ā<b>3</b> have been determined by single-crystal X-ray diffraction experiments: <b>1</b> is a mononuclear trigonal bipyramidal copper(II) species, <b>2</b> is a centrosymmetric oxalato-bridged dicopper(II) complex, and <b>3</b> consists of centrosymmetric tetranuclear units with intramolecular ironācopper and copperācopper distances around 5.010(1) and 5.1833(9) Ć
, respectively. Variable-temperature magnetic measurements of <b>2</b> and <b>3</b> were carried out from 50 to 350 (<b>1</b>) and 1.9 to 300Ā K (<b>3</b>). A strong antiferromagnetic interaction between copper(II) ions occurs in <b>2</b> (<i>J</i>Ā =Ā ā340Ā cm<sup>ā1</sup>, the spin Hamiltonian being defined as ). Analysis of the magnetic data of <b>3</b> shows magnetic interactions across the oxalate (<i>J</i><sub>1</sub>Ā =Ā ā341Ā cm<sup>ā1</sup>) and single cyanide (<i>J</i><sub>2</sub>Ā =Ā +12.9Ā cm<sup>ā1</sup>) ā¦ (<i>J</i><sub>2</sub>Ā =Ā +12.9Ā cm<sup>ā1</sup>) bridges . Simple symmetry considerations of the interacting magnetic orbitals in <b>2</b> and <b>3</b> provide a clear picture of the exchange pathways involved in these complexes.</p
Structural Invariance of a ZnII Coordination Polymer with 5-Aminoisophthalic Acid under Different Synthetic Conditions
<div><p>A same coordination polymer [Zn(aip)(DMSO)] (aip: 5-aminoisophthalate and DMSO: dimethylsulfoxide) was synthesized using the same reactants (ZnSO4, aip and H2O/DMSO) but in different conditions, in which the stoichiometry (1:1-4:1 metal:ligand ratio), temperature (70 and 100 Ā°C) and synthetic method (liquid-liquid diffusion, solvothermal and conventional with stirring) varied. A liquid assisted mechanochemical approach using ZnO as ZnII source instead ZnSO4, but keeping DMSO as milling liquid, also resulted in the same compound. This new coordination polymer was investigated using single-crystal X-ray diffraction technique, revealing a two-dimensional honeycomb-type network formation. The crystal structure was compared with either similar or isostructural compounds reported in the literature. Our studies show that the synthetic method and other synthetic variables do not affect the formation of [Zn(aip)(DMSO)] coordination polymers and probe the high stability (thermodynamic and kinetic) and structural invariance of this structure.</p></div
Lawsone Dimerization in Cobalt(III) Complexes toward the Design of New Prototypes of Bioreductive Prodrugs
Dimerization of lawsone occurs upon reaction with CoĀ(BF<sub>4</sub>)<sub>2</sub>Ā·6H<sub>2</sub>O and <i>N</i>,<i>N</i>ā²-bisĀ(pyridin-2-ylmethyl)Āethylenediamine (py<sub>2</sub>en) to produce the mononuclear complex [Co<sup>III</sup>(bhnq)Ā(py<sub>2</sub>en)]ĀBF<sub>4</sub>Ā·H<sub>2</sub>O (<b>1</b>). This
complex has been investigated as a prototype of a bioreductive prodrug,
where the bhnq<sup>2ā</sup> ligand acts as a model for cytotoxic
naphthoquinones. Cyclic voltammetry data in aqueous solution have
shown a <i>quasi</i>-reversible Co<sup>III</sup>/Co<sup>II</sup> process at <i>E</i><sub>1/2</sub> = ā0.26
V vs Fc/Fc<sup>+</sup>. Reactivity studies revealed the dissociation
of bhnq<sup>2ā</sup> from the complex upon reduction of <b>1</b> with ascorbic acid, and a dependence of the reaction rate
on the oxygen concentration suggests the occurrence of redox cycling
Lawsone Dimerization in Cobalt(III) Complexes toward the Design of New Prototypes of Bioreductive Prodrugs
Dimerization of lawsone occurs upon reaction with CoĀ(BF<sub>4</sub>)<sub>2</sub>Ā·6H<sub>2</sub>O and <i>N</i>,<i>N</i>ā²-bisĀ(pyridin-2-ylmethyl)Āethylenediamine (py<sub>2</sub>en) to produce the mononuclear complex [Co<sup>III</sup>(bhnq)Ā(py<sub>2</sub>en)]ĀBF<sub>4</sub>Ā·H<sub>2</sub>O (<b>1</b>). This
complex has been investigated as a prototype of a bioreductive prodrug,
where the bhnq<sup>2ā</sup> ligand acts as a model for cytotoxic
naphthoquinones. Cyclic voltammetry data in aqueous solution have
shown a <i>quasi</i>-reversible Co<sup>III</sup>/Co<sup>II</sup> process at <i>E</i><sub>1/2</sub> = ā0.26
V vs Fc/Fc<sup>+</sup>. Reactivity studies revealed the dissociation
of bhnq<sup>2ā</sup> from the complex upon reduction of <b>1</b> with ascorbic acid, and a dependence of the reaction rate
on the oxygen concentration suggests the occurrence of redox cycling
Alkaline Ion-Modulated Solid-State Supramolecular Organization in Mixed Organic/Metallorganic Compounds Based on 1,1ā²-Ethylenebis(4-aminopyridinium) Cations and Bis(oxamate)cuprate(II) Anions
Three new coordination compounds
of formula (edap)<sub>2</sub>Ā[CuĀ(opba)]<sub>2</sub>ĀĀ·4H<sub>2</sub>O (<b>1</b>), (edap)Ā[{Na<sub>2</sub>(H<sub>2</sub>O)<sub>4</sub>}Ā{Cu<sub>2</sub>(opba)<sub>2</sub>}]ĀĀ·2H<sub>2</sub>O (<b>2</b>), and (edap)Ā[{K<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>}Ā{Cu<sub>2</sub>(opba)<sub>2</sub>}]ĀĀ·3H<sub>2</sub>O (<b>3</b>) (edap = 1,1ā²-ethylenebisĀ(4-aminopyridinium)
and opba = 1,2-phenylenebisĀ(oxamate)) were synthesized through
the metathesis reaction involving A<sub>2</sub>[CuĀ(opba)] (A = Li<sup>+</sup>, Na<sup>+</sup>, and K<sup>+</sup>) and (edap)ĀCl<sub>2</sub>Ā·2H<sub>2</sub>O. Crystal structures of <b>1</b>ā<b>3</b> and edapĀ(IO<sub>3</sub>)<sub>2</sub>ĀĀ·4H<sub>2</sub>O compound were elucidated by single crystal X-ray diffraction. Compounds <b>1</b>ā<b>3</b> are built up from dinuclear copperĀ(II)
entities, {[CuĀ(opba)]<sub>2</sub>}<sup>4ā</sup> with an asymmetric
bisĀ(monatomic oxygen) bridge resulting from the parallel āout-of-planeā
disposition of the planar mononuclear [CuĀ(opba)]<sup>2ā</sup>. They possess distinct supramolecular arrangements of varying dimensionality
(<i>n</i>D with <i>n</i> = 0 (<b>1</b>),
1 (<b>2</b>), and 2 (<b>3</b>)) in the solid state depending
on the nature of the coordinated alkaline ion present alongside edap<sup>2+</sup> counterions. While the {[CuĀ(opba)]<sub>2</sub>}<sup>4ā</sup> building blocks are well-isolated in <b>1</b>, they form either
double chains or corrugated layers due to the coordination of the
Na<sup>+</sup> or K<sup>+</sup> ions in <b>2</b> and <b>3</b>, respectively. Magnetic properties of <b>1</b>ā<b>3</b> show a very weak antiferromagnetic coupling between the
Cu<sup>II</sup> ions through a double monatomic (Ī¼-O) bridge
(ā<i>J</i> = 1.63(9) (<b>1</b>), 2.29(2) (<b>2</b>), and 1.65(3) cm<sup>ā1</sup> (<b>3</b>)),
the Hamiltonian being defined as <i><b>H</b></i> =
ā(<i><b>S</b></i><sub><i><b>1</b></i></sub>Ā·<i><b>S</b></i><sub><i><b>2</b></i></sub>) + <i>g Ī²H</i>(<i><b>S</b></i><sub><i><b>1</b></i></sub> + <i><b>S</b></i><sub><i><b>2</b></i></sub>)
Tuning Photoluminescent Properties of Silver(I)-Based Coordination Networks through their Supramolecular Interactions
Eight
novel luminescent silverĀ(I)-based coordination networks have
been self-assembled from two flexible dicyanomethylene ligands bearing
diethylene (<b>L1</b>) and triethylene glycol (<b>L2</b>) spacers and silver salts (AgClO<sub>4</sub> or AgBF<sub>4</sub>) in dichloromethane/toluene or dichloromethane/benzene solvents.
Single-crystal X-ray diffraction reveals a variety of geometries around
the silverĀ(I) ion, resulting in mono-, bi-, and tetranuclear networks
with rare topologies. The coordination networks show two-dimensional
architectures through coordination of the cyano and glycolic groups
to the silverĀ(I) ions. The three-dimensional supramolecular arrangement
is formed through weak ĻĀ·Ā·Ā·Ļ and AgĀ·Ā·Ā·Ļ
interactions as well as hydrogen bonds between water molecules and
ClO<sub>4</sub><sup>ā</sup> and BF<sub>4</sub><sup>ā</sup> counterions. The silverĀ(I)-based coordination networks display green
to yellow emissions in the solid state, with quantum yields (Ī¦<sub>em</sub>) varying from 1.1 to 8.5%. The emission properties are attributed
to intraligand charge transfer and metal-perturbed intraligand transitions.
Supramolecular interactions, such as AgĀ·Ā·Ā·Ļ and
ĻĀ·Ā·Ā·Ļ interactions, play an important role
in the photophysical properties of these compounds
Influence of Synthetic Methods in the Structure and Dimensionality of Coordination Polymers
Eight
different coordination polymers (CPs) of Co<sup>2+</sup> and
Zn<sup>2+</sup> ions with rigid polycarboxylate ligands (fumaric acid
(<i>fum</i>) and 2,5-dihydroxyterephalic acid (<i>dhbdc</i>)) have been synthesized using the same solvents, stoichiometry,
and counterion but two different synthetic methods: liquidāliquid
diffusion methodāmethod A and pH control methodāmethod
B. The synthesis using method A resulted in four novel CPs: <i>trans</i>-CoĀ(dmso)<sub>2</sub>Ā(H<sub>2</sub>O)<sub>2</sub>Ā(fum)]<sub><i>n</i></sub> (<b>1</b>), [<i>trans</i>-ZnĀ(dmso)<sub>2</sub>Ā(H<sub>2</sub>O)<sub>2</sub>Ā(fum)]<sub><i>n</i></sub> (<b>2</b>), <i>trans</i>-CoĀ(dmso)<sub>2</sub>Ā(H<sub>2</sub>O)<sub>2</sub>Ā(dhbdc)]<sub><i>n</i></sub> (<b>3</b>), and [<i>trans</i>-ZnĀ(dmso)<sub>2</sub>Ā(H<sub>2</sub>O)<sub>2</sub>Ā(dhbdc)]<sub><i>n</i></sub> (<b>4</b>). Synthesis using method B resulted in one new ([ZnĀ(fum)Ā(OH)<sub>2</sub>] (<b>6</b>)) and three previously described CPs ([Co<sub>3</sub>(H<sub>2</sub>O)<sub>4</sub>Ā(OH)<sub>2</sub>Ā(fum)<sub>2</sub>]ĀĀ·2H<sub>2</sub>O (<b>5</b>), [Co<sub>2</sub>(dobdc)] (<b>7</b>), and [Zn<sub>2</sub>(dobdc)] (<b>8</b>), where <i>dobdc</i> = 2,5-dioxyterephtalic acid). The
new CPs (<b>1</b>ā<b>4</b>) were also structurally
investigated by single-crystal X-ray diffraction techniques, which
showed that all of them form one-dimensional (1D) CPs with linear
chain structure: it was evidenced that (<b>1</b>) and (<b>3</b>) are isomorphus crystals of (<b>2</b>) and (<b>4</b>), respectively. The crystal structures of <b>1</b>ā<b>4</b> were compared with similar 1D, two- and three-dimensional
(2D and 3D) CPs reported in the literature. Intra- and interchain
H-bond networks and coordination (<i>fum</i>, <i>dhbdc</i>, DMSO, water) as well as linkage (<i>fum</i> and <i>dhbdc</i>) isomerism guide the chain configuration (linear or
zigzag). It was also demonstrated that the new series of 1D CPs synthesized
here (<b>1</b>ā<b>4</b>) can work as precursors
for CP with higher dimensionality. Our studies showed that the synthetic
method plays a crucial role in the crystal growth of coordination
polymers
Crystal Engineering Applied to Modulate the Structure and Magnetic Properties of Oxamate Complexes Containing the [Cu(bpca)]<sup>+</sup> Cation
This
work deals with the crystal engineering features of four related
copperĀ(II)-based compounds with formulas {[{CuĀ(bpca)}<sub>2</sub>Ā(H<sub>2</sub>ppba)]Ā·1.33DMFĀĀ·0.66DMSO}<sub><i>n</i></sub> (<b>2</b>), [{CuĀ(bpca)Ā(H<sub>2</sub>O)}<sub>2</sub>Ā(H<sub>2</sub>ppba)] (<b>3</b>), [{CuĀ(bpca)}<sub>2</sub>Ā(H<sub>2</sub>ppba)]ĀĀ·DMSO (<b>4</b>), and
[{CuĀ(bpca)}<sub>2</sub>Ā(H<sub>2</sub>ppba)]ĀĀ·6H<sub>2</sub>O (<b>5</b>) [H<sub>4</sub>ppba = <i>N</i>,<i>N</i>ā²-1,4-phenylenebisĀ(oxamic acid) and Hbpca
= bisĀ(2-pyridylcarbonyl)Āamide] and how their distinct molecular and
crystal structures translate into their different magnetic properties. <b>2</b> and <b>3</b> were obtained through the hydrolytic
reaction of the double-stranded oxamato-based dipalladiumĀ(II) paracyclophane
precursor of formula [{K<sub>4</sub>(H<sub>2</sub>O)<sub>2</sub>}Ā{Pd<sub>2</sub>(ppba)<sub>2</sub>}] (<b>1</b>) with the mononuclear
copperĀ(II) complex [CuĀ(bpca)Ā(H<sub>2</sub>O)<sub>2</sub>]<sup>+</sup>, either in a waterāDMSOāDMF solvent mixture
or in water, respectively. The straightforward reaction of the neutral
H<sub>4</sub>ppba molecule with [CuĀ(bpca)Ā(H<sub>2</sub>O)<sub>2</sub>]<sup>+</sup> in a waterāDMSO mixture afforded compound <b>4</b>, whereas compound <b>5</b> resulted from the reaction
between the copperĀ(II) complex and the K<sub>2</sub>ppba salt in water.
The [Pd<sub>2</sub>(ppba)<sub>2</sub>]<sup>4ā</sup> tetraanionic
unit which is present in <b>1</b> has a [3,3] metallacyclophane-type
motif connected by two NāPdāN bonds. This entity acts
as a ligand toward partially hydrated potassiumĀ(I) cations through
its outer oxamate oxygens leading to a neutral three-dimensional network.
The structure of <b>2</b> consists of neutral chains made up
of double oxoĀ(carboxylate-oxamate)-bridged diĀ[{bisĀ(2-pyridylcarbonyl)Āamidate}ĀcopperĀ(II)]
units are which connected by the extended H<sub>2</sub>ppba<sup>2ā</sup> ligand, each of its oxamate fragments adopting a bidentate/outer
monodentate coordination mode. Compounds <b>2</b>ā<b>5</b> are neutral and centrosymmetric dicopperĀ(II) complexes which
have in common the presence of peripheral bpca ligands and H<sub>2</sub>ppba<sup>2ā</sup> as a bridge with each of its monoprotonated
oxamate groups exhibiting rare monodentate (<b>3</b>) and bis-bidentate
(<b>4</b> and <b>5</b>) coordination modes. Compounds <b>2</b>, <b>4</b>, and <b>5</b> share the same basic
[{CuĀ(bpca)}<sub>2</sub>Ā(H<sub>2</sub>ppba)] unit, but besides
the difference in the cocrystallization solvent molecules and synthetic
strategies, they feature very different crystal structures. To better
understand the role of palladiumĀ(II) ions in the formation of <b>2</b> and <b>3</b>, some studies were carried out using
different mixtures of solvents such as water, DMSO, and DMF which
revealed a major importance of DMF in the formation of <b>2</b> and the dependence on the palladiumĀ(II) ions in the formation of <b>3</b>. A reaction pathway leading to the formation of <b>2</b> and <b>3</b> is then proposed. The variable-temperature (2.0ā300
K) magnetic susceptibility measurements of <b>2</b>, <b>4</b>, and <b>5</b> revealed the occurrence of weak ferro- [<i>J</i> = +0.70 cm<sup>ā1</sup> (<b>2</b>)] and antiferromagnetic
interactions [<i>J</i> = ā0.90 (<b>4</b>) and
ā0.79 cm<sup>ā1</sup> (<b>5</b>)], the spin Hamiltonian
being defined as <b>H</b> = ā<i>J</i><b>S</b><sub>1</sub>Ā·<b>S</b><sub>2</sub>. The different
nature and strength of the magnetic coupling along this unique series
of compounds are discussed in the light of the structural data, and
they are compared with those of related dicopperĀ(II) systems
[Ag(L)NO<sub>3</sub>] Complexes with 2āBenzoylpyridine-Derived Hydrazones: Cytotoxic Activity and Interaction with Biomolecules
Complexes [AgĀ(H2BzPh)ĀNO<sub>3</sub>] (<b>1</b>), [AgĀ(H2Bz<i>p</i>CH<sub>3</sub>Ph)ĀNO<sub>3</sub>] (<b>2</b>), [AgĀ(H2Bz<i>p</i>ClPh)ĀNO<sub>3</sub>] (<b>3</b>), and [AgĀ(H2Bz<i>p</i>NO<sub>2</sub>Ph)ĀNO<sub>3</sub>] (<b>4</b>) were
synthesized with 2-benzoylpyridine benzoylhydrazone (H2BzPh) and its <i>para</i>-methyl-benzoylhydrazone (H2Bz<i>p</i>CH<sub>3</sub>Ph), <i>para</i>-chloro-benzoylhydrazone (H2Bz<i>p</i>ClPh), and <i>para</i>-nitro-benzoylhydrazone
(H2Bz<i>p</i>NO<sub>2</sub>Ph) derivatives. Experimental
data indicate that the nitrate ligand binds more strongly to the silver
center through one of the oxygen atoms, whereas the second oxygen
atom from nitrate and the hydrazone oxygen makes much weaker interactions
with the metal. Dissociation of nitrate most probably occurs in solution
and in biological media. Interestingly, theoretical calculations suggested
that when dissociation of the nitrate takes place, all bond orders
involving the metal and the atoms from the hydrazone ligand increase
significantly, showing that the bonding of nitrate results in the
weakening of all other interactions in the metal coordination sphere.
Upon complexation of the hydrazones to silverĀ(I), cytotoxicity against
B16F10 metastatic murine melanoma cells increased in all cases. Complexes
(<b>1ā3</b>) proved to be more cytotoxic than cisplatin.
All compounds were more cytotoxic to B16F10 cells than to nontumorigenic
murine Melan-A melanocyte cells. Interestingly, the selectivity index
(SI = IC<sub>50Ā nonāmalignantĀ cells</sub>/IC<sub>50Ā tumorĀ cells</sub>) of complex (<b>1</b>), SI =
23, was much higher than that of the parent hydrazone ligand, SI =
9.5. Studies on the interactions of complexes (<b>1ā3</b>) with DNA suggested that although (<b>1ā3</b>) interact
with calf thymus DNA by an intercalative mode, direct covalent binding
of silverĀ(I) to DNA probably does not occur. Complexes (<b>1ā3</b>) interact in vitro with human serum albumin indicating that these
compounds could be transported by albumin
A Two-Dimensional Oxamate- and Oxalate-Bridged Cu<sup>II</sup>Mn<sup>II</sup> Motif: Crystal Structure and Magnetic Properties of (Bu<sub>4</sub>N)<sub>2</sub>[Mn<sub>2</sub>{Cu(opba)}<sub>2</sub>ox]
A new compound of formula (Bu<sub>4</sub>N)<sub>2</sub>[Mn<sub>2</sub>{CuĀ(opba)}<sub>2</sub>ox] (<b>1</b>) [Bu<sub>4</sub>N<sup>+</sup> = tetra-<i>n</i>-butylammonium cation, H<sub>4</sub>opba = 1,2-phenylenebisĀ(oxamic
acid), and H<sub>2</sub>ox
= oxalic acid] has been synthesized and magneto-structurally investigated.
The reaction of manganeseĀ(II) acetate, [CuĀ(opba)]<sup>2ā</sup>, and ox<sup>2ā</sup> in dimethyl sulfoxide yielded single
crystals of <b>1</b>. The structure of <b>1</b> consists
of heterobimetallic oxamato-bridged Cu<sup>II</sup>Mn<sup>II</sup> chains which are connected through bis-bidentate oxalate coordinated
to the manganeseĀ(II) ions to afford anionic heterobimetallic layers
of 6<sup>3</sup>-hcb net topology. The layers are interleaved by <i>n</i>-Bu<sub>4</sub>N<sup>+</sup> counterions. Each copperĀ(II)
ion in <b>1</b> is four-coordinate in a square planar environment
defined by two amidate-nitrogen and two carboxylate-oxygen atoms from
the two oxamate groups of the obpa ligand. The manganeseĀ(II) ion is
six-coordinate in a somewhat distorted octahedral surrounding that
is built by two oxalate-oxygen and four carbonyl-oxygen atoms from
two [CuĀ(opba)]<sup>2ā</sup> units. The magnetic properties
of <b>1</b> in the temperature range 1.9ā300 K correspond
to those expected for the coexistence of intralayer antiferromagnetic
interactions of the type copperĀ(II)āmanganeseĀ(II) across oxamato
and manganeseĀ(II)āmanganeseĀ(II) through oxalato bridges plus
a weak spin canting in the very low temperature domain. Simulation
of the magnetic data through quantum Monte Carlo methodology reveals
the magnitude of the intralayer magnetic interactions [<i>J</i><sub>CuMn</sub> = ā32.5(3) cm<sup>ā1</sup>, and <i>J</i><sub>MnMn</sub> = ā2.7(3) cm<sup>ā1</sup>], their values being within the range of those previously observed
in lower nuclearity systems