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PubMed2002

Inhibition of the potassium current IK(SO), in cerebellar granule cells, by the inhibitors of MEK1 activation, PD 98059 and U 0126.

IK(SO) is a standing-outward potassium current found in cerebellar granule neurons which is inhibited by the activation of muscarinic M(3) receptors. However the pathway between muscarinic receptor activation and current inhibition is unknown. Using two structurally distinct inhibitors of the activation of MEK1 (mitogen activated protein (MAP) kinase kinase 1), PD 98059 and U 0126, we have shown that the MAP kinase signalling cascade does not appear to underlie muscarinic inhibition of IK(SO), recorded using whole-cell patch-clamp methods. Nevertheless, both PD 98059 and U 0126 caused an inhibition of IK(SO) when applied acutely with 30 microM of each compound producing around 50% inhibition of the current. In addition, U 0125, which is structurally related to U 0126 but has a much lower potency for inhibiting MEK1 activation, was also able to inhibit IK(SO) to a similar degree. Neither the inhibition by PD 98059 nor that by U 0126 was found to be voltage dependent. This was true whether the IK(SO) current was outward or inward. Block of IK(SO) by these two compounds may compromise interpretation of studies in intact neuronal preparations when they are used as MEK1 inhibitors.

Animals↗
PubMed2003

Anthropogenic platinum group element (Pt, Pd and Rh) concentrations in road dusts and roadside soils from Perth, Western Australia.

The emission of platinum group elements (PGE) from automobile catalytic converters has led to rapid increases in Pt, Pd and Rh concentrations in roadside media. This article represents the first detailed study to assess PGE levels in road dusts and roadside soils in Australia. Road dust and roadside soil samples were analysed by ICP-MS following microwave digestion and cation exchange. All samples show elevation of PGE above average upper crust values, with maximum values of 420 ng g(-1) Pt, 440 ng g(-1) Pd and 91 ng g(-1) Rh. PGE ratios in road dusts and soils are consistent with known catalytic converter compositions and while Pt and Rh abundances are comparable with European studies, Pd levels are substantially higher in Australian samples. PGE in these samples are not correlated with Pb, though positive correlations with Ce, Cu and Y are evident. No straightforward relationship between traffic volume and PGE abundance is evident and factors such as driving style, topography, road drainage and potentially climate exert considerable influences.

Journal Article↗
PubMed1996

Acquisition of conditioned reward blocked by intra-accumbens infusion of PD-140548, a CCKA receptor antagonist.

Cholecystokinin (CCK) is an endogenous peptide that is colocalized with dopamine (DA) in some mesolimbic neurons projecting to the nucleus accumbens (NAC). DA has been implicated in the acquisition of conditioned rewarding properties by neutral stimuli [conditioned stimuli (CS)] associated with a primary reward (such as food). A variety of experimental evidence suggests that exogenously applied CCK, acting at the CCKA receptor, potentiates the function of DA in the NAC. Thus, the present experiment examined the role of endogenous CCKA mechanisms in the NAC in the development of conditioned reward. The CCKA receptor-selective antagonist PD-140548 was microinjected into the NAC during the CS-food pairing phase of a conditioned reward experiment. In the test session, animals that previously received vehicle microinjections into the NAC or PD-140548 microinjections into areas surrounding the NAC pressed a lever that produced the CS more often than did a control lever. The CS had gained conditioned rewarding properties. However, animals that received PD-140548 microinjections into the NAC did not exhibit a preference for the CR lever. Results suggest that blockade of CCKA receptors in the NAC impairs the development of conditioned reward. These findings support a role for endogenous CCKA mechanisms in the NAC in the acquisition of stimulus-reward associations.

Animals↗
PubMed1998

Pharmacological characterization of PD 152255, a novel dimeric benzimidazole dopamine D3 antagonist.

152255 (E-1,1'-(2-butene-1,4-diyl)bis[2-[4-[3-(1-piperidinyl)propoxy]-phe nyl]-1H-benzimidazole]) exhibited high affinity (Ki = 12.7 nM) for human dopamine (DA) D3 receptors expressed in CHO K1 cells but not for DA D2L receptors (Ki = 565 nM), DA D42 or DA D1 receptors (Ki > 3 microM) and a number of other neurotransmitter receptors. Affinity for human muscarinic receptors was seen in vitro but no functional muscarinic agonist and/or antagonist action was observed in vivo. Antagonist activity at DA D3 receptors was demonstrated by blockade of quinpirole-stimulated [3H]-thymidine uptake in D3 transfected cells, an effect that was 28-fold more potent than in D2-transfected cells. Unlike classical DA D2 antagonists, PD 152255 did not increase rat brain DA synthesis and it increased locomotion in habituated rats. However, like antipsychotics, PD 152255 reduced locomotor activity in mice and reduced spontaneous and amphetamine-stimulated locomotion in nonhabituated rats. These results demonstrate that PD 152255 is a DA D3 antagonist that may have antipsychotic activity.

Animals↗
PubMed1982

Preliminary studies on the inhibitory effect of novel Pd(II) complexes of vitamin B6 on cell divisions.

Two novel complexes of Pd(II) involving vitamin B6 compounds have been synthesized. They are compatible with the compositions Pd(P.H.)2 C2(P = pyridoxol) and Pd(PL.H)2 C2(PL = pyridoxal). The complexes inhibited the growth as well as the biosynthesis of RNA, DNA, and protein of E. coli B-766. Photoacoustic spectral (PAS) measurements showed that the complexes bound to DNA of the bacteria and were present only in the kidney of treated mice. The complexes inhibited the incorporation of 3H-thymidine as well as 14C-leucine in the DNA and protein, respectively, of liver cell cultures (BL8L). The inhibition of cell division of Walker-S-cells and human lymphocytes by the complexes was highly significant.

Animals↗
PubMed2003

Lipid solubility of the platinum group metals Pt, Pd and Rh in dependence on the presence of complexing agents.

Investigations on the bioaccumulation of the platinum group metals (PGM) Pt, Pd and Rh in aquatic organisms are of growing interest in environmental research due to the increasing emission of these metals by motor vehicles with catalytic converters. Until now, nothing is known about the possible influence of complexing agents on the bioaccumulation capacity of these precious metals. According to the partition coefficient between 1-octanol and water (POW) as a measure of bioaccumulation, in this study a simple shaking method was performed in order to investigate the effects of different complexing agents (-methionine, thio urea, EDTA, humic substances, bile compounds) on the octanol solubility of the PGM. The results demonstrated a significant influence of all agents used. -Methionine and thio urea decreased the lipid solubility. In contrast, the presence of EDTA, humic substances and especially bile caused a higher transfer of metals in the octanol phase. For most complexing agents tested, the transfer of Pd to the lipid phase was significantly higher compared with Rh and Pt, except for bile acid where the highest octanol solubility was found for Pt. Recent experimental results on PGM accumulation in zebra mussels confirm a high bioaccumulation of Pd which could be predicted from the lipid solubility.

Air Pollutants↗
PubMed2002

Differential effects of the CCKA receptor ligands PD-140,548 and A-71623 on latent inhibition in the rat.

Latent inhibition (LI) is a behavioural paradigm in which repeated exposure to a stimulus without consequence inhibits the formation of any new associations with that stimulus. To the extent that LI reflects a process of leaming to ignore irrelevant stimuli, disrupted LI has been suggested as an animal model for the attentional deficits observed in schizophrenia. The antipsychotic potential of cholecystokinin (CCK) stems from its colocalization with dopamine (DA) in the mesolimbic pathway, where it demonstrates both excitatory and inhibitory effects on dopaminergic activity. This may be explained by mediation through different receptor subtypes. A variety of hypotheses has emerged regarding the potential clinical application of subtype-selective CCK-based drugs. The present experiments examined the effects on LI of two selective CCK(A) ligands: PD-140,548 (a CCK(A) antagonist, Experiment 1: 0.001, 0.01, and 0.1 mg/kg) and A-71623 (a CCK(A) agonist, Experiment 2: 0.02, 0.05, and 0.1 mg/kg). In both experiments, the effects of haloperidol (0.1 mg/kg) were also investigated. Animals receiving 0.1 mg/kg of haloperidol or 0.001 or 0.1 mg/kg (but not 0.01 mg/kg) of PD-140,548 treated the preexposed stimulus as irrelevant after a low number of preexposures. In contrast, no facilitatory effect on LI was detectable at any of the A-71623 doses. The finding that A-71623 failed to enhance LI indicates that it is unlikely that this compound would have any antipsychotic effect within the clinical setting. Considering the facilitatory effect exerted by PD-140,548 on LI, it is probable that the inhibition of CCK activity might prove a more promising strategy for the pharmacological treatment of schizophrenia.

Animals↗
PubMed1998

Expression of platelet-derived endothelial cell growth factor (PD-ECGF) and its mRNA in uterine endometrial cancers.

To determine the potential of growth, invasion and metastasis of uterine endometrial cancer cells associated with neovascularization, the expressions of platelet-derived endothelial cell growth factor (PD-ECGF) and its mRNA in uterine endometrial cancers and in normal uterine endometria as controls were determined and the relationship between their expressions and histological grades, grades of myometrial invasion and clinical stages of uterine endometrial cancers was analyzed. The levels of PD-ECGF were significantly higher in uterine endometrial cancers of well-differentiated grade (G1) with invasion to < or =1/2 myometrium (B) and of stage 1 than in those of moderately and poorly differentiated grades (G2 and G3, respectively) limited to endometrium (A) and with invasion to >1/2 myometrium (C) and of stages II and III/IV and in normal uterine endometria. There was no significant difference in the levels between uterine endometrial cancers of G2 and G3, A and C, or stages II and III/IV and normal uterine endometria. Therefore, the active availability of PD-ECGF might contribute to the acceleration of angiogenic activity in the early process of invasion of well-differentiated uterine endometrial cancers.

Adult↗
PubMed2006

Fabrication and characterization of nanostructured Pd hydride pH microelectrodes.

Novel pH microsensors were made by electrodepositing mesoporous Pd films onto Pt microdisks, electrochemically loading the films with hydrogen to form the alpha+beta Pd hydride phase, and then switching to the potentiometric mode to monitor pH. To create a nanostructure, the films were deposited within a molecular template formed by the self-assembly of surfactant molecules, a technique known as true liquid crystal templating. The films retain the micrometer size of the Pt microdisk but offer electroactive areas up to 900 times larger. Optimum hydrogen loading conditions were determined, and the mesoporous Pd microdisks were found to have excellent potentiometric properties. From pH 2 to 12, their potential was Nernstian, highly reproducible, very stable (+/-1.2 mV over 2 h), and without hysteresis. Their response time was better than 1 s. However, the presence of oxygen reduced their lifetime significantly, thereby requiring frequent reloading. These microelectrodes do not require calibration before and after measurements, a procedure normally essential for potentiometric pH microsensors. To our knowledge, these are the first results where nanostructured materials made by the true liquid crystal templating method have been used in the potentiometric mode; moreover, these are the first results demonstrating the application of nanostructured microdisks in the potentiometric mode.

Journal Article↗
PubMed2001

Pd-catalyzed TCE dechlorination in water: effect of [H2](aq) and H2-utilizing competitive solutes on the TCE dechlorination rate and product distribution.

The aqueous-phase H2 concentration ([H2](aq)) and the presence of H2-utilizing competitive solutes affect TCE dechlorination efficiency in Pd-based in-well treatment reactors. The effect of [H2](aq) and H2-utilizing competing solutes (cis-DCE, trans-DCE, 1,1-DCE, dissolved oxygen (DO), nitrite, nitrate) on the TCE transformation rate and product distribution were evaluated using 100 mg/L of a powdered Pd-on-Al2O3 catalysts in batch reactors or 1.0 g of a 1.6-mm Pd-on-gamma-Al2O3 catalyst in column reactors. The TCE dechlorination rate constant decreased by 55% from 0.034 +/- 0.006 to 0.015 +/- 0.001 min-1 when the [H2](aq) decreased from 1000 to 100 microM and decreased sharply to 0.0007 +/- 0.0003 min-1 when the [H2](aq) decreased from 100 to 10 microM. Production of reactive chlorinated intermediates and C4-C6 radical coupling products increased with decreasing [H2](aq). At an [H2](aq) of 10 microM (P/Po = 0.01), DCE isomers and vinyl chloride accounted for as much as 9.8% of the TCE transformed at their maximum but disappeared thereafter, and C4-C6 radical coupling products accounted for as much as 18% of TCE transformed. The TCE transformation rate was unaffected by the presence of cis-DCE (202 microM), trans-DCE (89 microM), and 1,1-DCE (91 microM), indicating that these compounds do not compete with TCE for catalyst active sites. DO is twice as reactive as TCE but had no effect on TCE conversion in the column below a concentration of 370 microM (11.8 mg/L), indicating that DO and TCE will not compete for active catalyst sites at typical groundwater DO concentrations. TCE conversion in the column was reduced by as much as a factor of 10 at influent DO levels greater than 450 mM (14.3 mg/L) because the [H2](aq) fell below 100 microM due to H2 utilized in DO conversion. Nitrite reacts 2-5 times slower than TCE and reduced TCE conversion by less than 4% at a concentration of 6630 microM (305 mg/L). Nitrate was not reactive and did not effect TCE conversion at a concentration of 1290 microM (80 mg/L).

Chlorine Compounds↗
PubMed2001

Heterodi- [MAg, MAu (M = Pd, Pt)], Tri- [PdAg(2), PtAg(2), PtAu(2), Pt(2)M (M = Ni, Pt, Cd, Hg)], and Tetranuclear (Pt(2)Ag(2), Pt(2)Au(2)) 1,1-ethylenedithiolato complexes.

The reactions of [M(PPh(3))(2)[S(2)C=C[C(O)Me](2)]] [M = Pd (1a), Pt (1b)] with AgClO(4) and PPh(3) or with [Au(PPh(3))(OCMe(2))]ClO(4) afford heterodinuclear [[M(PPh(3))(2)][M'(PPh(3))][S(2)C=C[C(O)Me](2)]]ClO(4) [M = Pd, M' = Ag (2a), M = Pt, M' = Ag (2b), Au (4)] or trinuclear [[M(PPh(3))(2)][M'(PPh(3))](2)[S(2)C=C[C(O)Me](2)]](ClO(4))(2) [M = Pd, M' = Ag (3a), M = Pt, M' = Ag (3b), Au (5)] 1,1-ethylenedithiolato complexes, depending on the molar ratio of the reagents. We have recently reported that, in the absence of added PPh(3), the reactions of [Pt[S(2)C=C[C(O)Me](2)]L(2)] [L = PPh(3) (1b), L(2) = 1,5-cyclooctadiene (cod) (1c)] with AgClO(4) produce the heterotetranuclear derivatives [[PtL(2)](2)Ag(2)[S(2)C=C[C(O)Me](2)](2)]](ClO(4))(2) [L = PPh(3) (6a), L(2) = cod (6b)], which have been used now as efficient transmetallating agents toward gold, platinum, mercury, nickel, copper, or cadmium metal centers to give new types of 1,1-ethylenedithiolato complexes: [[Pt(PPh(3))(2)](2)Au(2)[S(2)C=C[C(O)Me](2)](2)](ClO(4))(2) (7), [(PtL(2))(2)M[S(2)C=C[C(O)Me](2)](2)](ClO(4))(2) [L(2) = cod, M = Pt (8), L = PPh(3), M = Hg (9)], [[Pt(PPh(3))(2)](2)[S(2)C=C[C(Me)=O](2)](2)Ni](ClO(4))(2) (10), and [[Pt(PPh(3))(2)](2)[S(2)C=C[C(Me)=O](2)](2)[M(OClO(3))(2)]] [M = Cu (11), [C(O)Me](2)] moieties but, whereas in 7 they bridge two gold(I) centers through the sulfur atoms, in 11 they chelate the copper(II) center through the oxygen atoms. The last one is the first example of such a coordination mode for the 2,2-diacetyl-1,1-ethylenedithiolato ligand.

Journal Article↗
PubMed2002

Thermodynamic and kinetic control over the reduction mechanism of the Pd(3)(dppm)(3)(CO)(I)(+) cluster.

The reduction mechanism of the title cluster has been investigated by means of cyclic voltammetry (CV), rotating disk electrode (RDE) voltammetry, and coulometry. The 2-electron reduction proceeds via two routes simultaneously. The first one involves two 1-electron reduction steps, followed by an iodide elimination to form the neutral Pd(3)(dppm)(3)(CO)(0) cluster (EEC mechanism). The second one is a 1-electron reduction process, followed by an iodide elimination, then by a second 1-electron step (ECE mechanism) to generate the same final product. Control over these two competitive mechanisms can be achieved by changing temperature, solvent polarity, iodide concentration, or sweep rate. The reoxidation of the Pd(3)(dppm)(3)(CO)(0) cluster in the presence of iodide proceeds via a pure ECE pathway. The overall results were interpreted with a six-member square scheme, and the cyclic and RDE voltammograms were simulated, in order to extract the reaction rate and equilibrium constants for iodide exchange for all three Pd(3)(dppm)(3)(CO)(I)(n)() (n = +1, 0, -1) adducts.

Journal Article↗
PubMed2003

A complete family of isostructural cluster compounds with cubane-like M(3)S(4)M' cores (M = Mo, W; M' = Ni, Pd, Pt): comparative crystallography and electrochemistry.

By reaction of the geometrically incomplete cubane-like clusters [(eta(5)-Cp')(3)Mo(3)S(4))][pts] and [(eta(5)-Cp')(3)W(3)S(4)][pts] (Cp' = methylcyclopentadienyl; pts = p-toluenesulfonate) with group 10 alkene complexes, three new heterobimetallic clusters with cubane-like cluster cores were isolated: [(eta(5)-Cp')(3)W(3)S(4)M'(PPh(3))][pts] ([5][pts], M' = Pd; [6][pts], M' = Pt); [(eta(5)-Cp')(3)Mo(3)S(4)Ni(AsPh(3))][pts] ([7][pts]). The compounds [5][pts]-[7][pts] are completing the extensive series of clusters [(eta(5)-Cp')(3)M(3)S(4)M'(EPh(3))][pts] (M = Mo, W; M' = Ni, Pd, Pt; E = P, As) which allows the consequences of replacing a single type of atom on structural and NMR and UV/vis spectroscopic as well as electrochemical properties to be determined. Single-crystal X-ray structure determinations of [5][pts]-[7][pts] revealed that [5][pts] was not isomorphous to the other members of the series [(eta(5)-Cp')(3)M(3)S(4)M'(EPh(3))][pts] due to distinctly different cell parameters, which in the molecular structure of [5](+) is reflected in a slightly different orientation of the PPh(3) ligand. Electrochemical measurements on the series showed that the Mo-based clusters were more difficult to oxidize than their W-based analogues. The Pd-containing clusters underwent two-electron oxidation processes, whereas the Ni- and Pt-containing clusters underwent two separated one-electron oxidation processes.

Journal Article↗
PubMed2002

Ion pair charge-transfer complexes between anionic and cationic metal-dithiolenes [M(II) = Pd, Pt].

New [M(R(2)pipdt)(2)](BF(4))(2) salts [R(2)pipdt = N,N'-dialkyl-piperazine-2,3-dithione; M = Pd(II), R = Me and M = Pt(II), R = Me, Et, Pr(i)] bearing redox-active cationic dithiolene complexes have been prepared and characterized. These cations react with the redox-active [M(mnt)(2)](2-) [M = Pd(II), Pt(II); mnt = maleonitrile-2,3-dithiolate] anionic dithiolenes to form salts describable as ion pair charge-transfer complexes. X-ray crystallographic studies have shown that [M(Me(2)pipdt)(2)][M(mnt)(2)] complexes, with M = Pd(II) and Pt(II), are isomorphous. Crystal data of the Pt salt (3a): triclinic, Ponemacr; (No. 2); Z = 1; T = 293(2) K; a = 6.784(7) A, b = 8.460(6) A, c = 13.510(5) A, alpha = 100.63(2) degrees, beta = 104.04(2) degrees, gamma = 96.90(2) degrees; R1 = 0.0691 [wR2 = 0.2187 (all data)]. Structural data show that approximately square-planar [Pt(Me(2)pipdt)(2)] dications and regular square-planar [Pt(mnt)(2)] dianions form an infinite anion-cation one-dimensional stack along axis a with a Pt...Pt a/2 distance of 3.392 A and a Pt...Pt...Pt angle of 180 degrees. Anions and cations arrange themselves face-to-face so as to take on a staggered arrangement. These salts exhibit strong absorptions in the visible-near-infrared region assigned to ion pair charge-transfer transitions. A relation between the optical and thermal electron transfer in the solid state is obtained using a "Marcus-Hush model", and a solid-state electrical conductivity in agreement with expectations is observed. Vibrational spectroscopy is in agreement with the existence of charge-transfer interactions between the cationic and anionic components of the salts.

Journal Article↗
PubMed2004

Does alpha-fluorination affect the structural trans-influence and kinetic trans-effect of an alkyl ligand? Molecular structures of Pd(TMEDA)(CH(3))(R(F)) and a kinetic study of the trans to cis isomerization of Pt(TMEDA)(CH(3))(2)I(R(F)) [R(F) = CF(2)CF(3), CFHCF(3), CH(2)CF(3)].

Reaction of Pd(TMEDA)(CH(3))(2) [TMEDA = tetramethylethylenediamine] with fluoroalkyl iodides R(F)I affords a series of square planar Pd(II) complexes Pd(TMEDA)(CH(3))(R(F)) [R(F) = CF(2)CF(3) (9), CFHCF(3) (10), CH(2)CF(3) (11)], presumably by oxidative addition followed by reductive elimination of CH(3)I. The solid-state structures of each compound have been determined by single crystal X-ray diffraction studies, allowing the effect of increasing alpha-fluorination on the structural trans-influence of alkyl ligands to be examined. In these compounds there is no significant difference observed in the trans-influence of the three fluorinated alkyl ligands toward the trans-N atom, although a significant cis-influence on the neighboring methyl ligand is apparent. Oxidative addition of the same series of fluoroalkyl ligands to the corresponding Pt(TMEDA)(CH(3))(2) affords octahedral Pt(IV) complexes trans-Pt(TMEDA)(CH(3))(2)(R(F))I [R(F) = CF(2)CF(3) (12), CFHCF(3) (13), CH(2)CF(3) (14)] as the kinetic products. In each case, subsequent isomerization to the corresponding all cis-isomers is observed; in the case of 13, the stereocenter at the alpha-carbon results in two diastereomeric cis-isomers, which are formed at different rates. The molecular structures of 13 and its more stable all cis-isomer 16b have been crystallographically determined. Kinetic studies of the trans-cis isomerization reactions show the mechanism to involve a polar transition state, presumably involving iodide dissociation, followed by rearrangement of the cation, and iodide recombination. High dielectric solvents increase the rate, but solvent coordinating ability has no effect. Dissolved salts (LiI, LiOTf) show normal accelerative salt effects, with no inhibition in the case of added iodide, consistent with the formation of an intimate ion pair intermediate. The kinetic parameters show that the trans-effects of fluoroalkyl ligands in these compounds follow the order expected from the relative sigma-donor properties of the ligands, with CF(2)CF(3) < CFHCF(3) < CH(2)CF(3).

Journal Article↗
PubMed2004

Synthesis and characterization of Pd(II) Complexes with bis-pyridinium and isoquinolinium N-ylides: moderate C-H...O=C intramolecular hydrogen bonds as source of conformational preferences.

The bis(N-ylide) Pd(II) complexes cis-[PdX2[eta2-[C(H)NCxHy]2CO]] (X=I, NCxHy=NC5H5, 2a; X=Br, NCxHy=NC5H5 and NC5H3-2,3-Me2, 2c, isoquinolinium NC9H7, 2d) have been prepared by reaction of the corresponding bis-pyridinium salts with Pd(OAc)2 (1:1 molar ratio). Compounds 2 react with AgClO4 and Tl(acac) (1:1:1 molar ratio) to give the acetylacetonato derivatives [Pd(acac-O,O'[eta2-[C(H)NCxHy]2CO]]ClO4 (3a, c, d). In compounds 2 and 3, the bis-ylide is bonded as a C,C-chelate ligand through the two ylidic Calpha atoms. The reaction is stereoselective, and only one diastereoisomer is observed (meso form, RS/SR). The origin of the observed stereoselectivity lies with the establishment of intramolecular C-H...O=C hydrogen bonds between the ortho protons of the pyridine or isoquinoline fragments and the carbonyl oxygen, as it has been shown by density functional theory (DFT) calculations (B3LYP level) and Bader analysis of the electron density on model pyridinium ylides. Despite the inherent weakness of the C-H...O=C bonds, the results show that in these N-ylides the hydrogen bonds are stronger than expected and should be classified as moderate H bonds.

Journal Article↗
PubMed2006

Synthesis, cytotoxic effect, and structure-activity relationship of Pd(II) complexes with coumarin derivatives.

We report the influence of the substituent at the N atom of the ligands on the synthesis, biological activity, and stability of Pd(II) complexes of the general formula PdL(2). The compounds adopt a cis or trans configuration with respect to the substituent at the nitrogen atom. Sterically hindered substituents promote the formation of trans isomers, whereas when the nitrogen atom is unsubstituted, cis isomers are formed. The compounds were characterized by elemental analysis, infrared and 1H NMR spectroscopies, and electrospray mass spectrometry. The complexes were also studied using X-ray diffraction and computational DFT methods. Both complexes cis-3a and trans-3c exhibit square-planar geometries around the Pd(II) atom. The cytotoxic effects of these complexes were examined on two human leukemia cell lines, HL-60 and NALM-6. Pd complex cis-3a showed significant cytotoxic activity. The effects exhibited by this complex were comparable to those reported for carboplatin. Loigand 2a was not cytotoxic. Computational analysis carried out at the PB/B3LYP/LACVP**//mPW1PW91/LanL2DZ level showed excellent correlation between the energy difference of the cis and trans isomers and the cytotoxic activity, rendering computations a useful predictive tool for the design of new drugs.

Antineoplastic Agents↗
PubMed2006

Bimetallic clusters of iron with palladium and platinum. Synthesis and structures of Fe2(CO)9[M(PBu(t)3)]2 (M = Pd or Pt) and Fe2(CO)8[Pt(PBu(t)3)]2(mu-H)2.

The reaction of Fe2(CO)9 with Pd(PBu(t)3)2 and Pt(PBu(t)3)2 yielded the Fe-Pd and Fe-Pt cluster complexes Fe2(CO)9[M(PBu(t)3)]2, M = Pd (8) or Pt (9). The structures of 8 and 9 are analogous and consist of nearly planar butterfly clusters of two palladium/platinum atoms in the wing-tip positions and two mutually bonded iron atoms, Fe-Fe = 2.9582(11) A in 8 and 2.9100 (9) A in 9. Compound 8 decomposes to form the mononuclear iron compound Fe(CO)4(PBu(t)3) (11) when heated at 68 degrees C. The reaction of Pt(PBu(t)3)2 with Fe2(CO)9 in the presence of hydrogen at 127 degrees C yielded the dihydrido complex Fe2(CO)8[Pt(PBu(t)3)]2(mu-H)2 (10). Compound 10 contains a closed Fe2Pt2 tetrahedral cluster with hydrido ligands bridging two of the Fe-Pt bonds. Compounds 8, 9, and 10 were structurally characterized crystallographically.

Journal Article↗