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Experimental charge-density study on the nickel(II) coordination complex [Ni(H3L)][NO3][PF6] [H3L = N,N',N''-tris(2-hydroxy-3-methylbutyl)-1,4,7-triazacyclononane]: a reappraisal.

The experimental charge density in the title complex has been re-examined. The original work, reported some 8 years ago [Smith et al. (1997). J. Am. Chem. Soc. 119, 5028-5034], was undertaken using a very early version of the XD software, which contained serious programming errors. A re-refinement, using the original data and a recent version of the XD software, shows that many of the unusual aspects of this earlier study are artefacts due to these programming errors. The topological properties of the newly obtained experimental density compare well with those calculated from a theoretical DFT (density-functional theory) UHF-SCF (unrestricted Hartree Fock-self-consistent field) density. This report corrects several erroneous conclusions regarding the charge density in the title complex--in particular, the highly unusual diffuse Laplacian distribution about the Ni atom, and the trifurcated bond path from the Ni atom to the alcohol oxygen donor atoms are no longer observed. An examination of a range of topological properties of the metal-ligand bonds leads to the conclusion that the Ni-N and Ni-O bonds have an intermediate character, with a significant shared interaction, but with a substantial ionic component. This new study also reveals a previously unrecognized intramolecular H...H interaction in the macrocyclic ligand.

Journal Article↗

Fibrinogen from human plasma: preparation by precipitation with heavy-metal coordination complex.

Potassium tetrathiocyanato-(S)mercurate II [K(2)Hg(SCN)(4)] is used in a mild and rapid procedure for the isolation of human fibrinogen from fresh plasma. The final product, 94 to 99 percent of which is coagulable by thrombin, represents an average yield of 80 percent and is stable in solution. It is free of plasmin, streptokinase-activatable plasminogen, and coagulation factors II, V, VIII, X and XIII. Sedimentation analysis reveals a single peak with a sedimentation coefficient equal to 7.0S at infinite dilution. Immunodiffusion on cellulose acetate results in two precipitin lines with rabbit antiserum to whole human serum. The fibrinogen precipitates are unusual in that they are flocculent and readily redissolve.

Animals↗

Molecular mechanics aided design of antineoplastic agents from ruthenium coordinate complexes.

Through energy minimization using molecular mechanics force field four ruthenium cordinate complexes have been synthesized. Compound I to IV showed antineoplastic activity with varying degree on EAC bearing mice. Mode of action may be through inhibition of antioxidant property of tumor cell as evident from lipid peroxidase activity. Among the complexes Bis pyridine tetrachloro ruthenium exhibits highest order of activity with respect to increase mean survival time, inhibition of tumour volume, total blood count, hemoglobin and lipid peroxidase activity.

Animals↗

Review of the current clinical status of platinum coordination complexes in cancer chemotherapy.

During the past 3 years, eight hospitals and one cooperative study group have reported their initial clinical results with cis-dichlorodiammineplatinum (II). The most popular clinical schedule was 15-25 mg/m2/day for 5 days repeated every 3-4 weeks. Almost all patients had extremely advanced disease. Of 323 patients in whom response could be evaluated, there were 12 complete responses, 25 partial responses (greater than 50% decrease in tumor size), and 23 improvements (greater than 50% decrease in tumor size) for a 19% overall response rate. The tumor most sensitive to cis-dichlorodiammineplatinum (II) was testicular carcinoma in which seven complete responses, three partial responses, and three improvements were observed in 16 patients treated at Roswell Park Memorial Institute. Other sensitive tumors were lymphoma (63% response and improvements), squamous cell carcinoma of the head and neck (41% response and imporvements), and ovarian carcinoma (40% response and improvements). Complete responses were also seen in one patient with thyroid carcinoma and two with bladder carcinoma, while partial remissions were recorded in two patients with breast carcinoma and one patient each with acute myelogenous leukemia, endometrial carcinoma, renal carcinoma, malignant thymoma, neuroblastoma, adenocarcinoma of the lung, and an undifferentiated tumor of unknown origin. Five major types of toxicity were encountered: gastrointestinal, hematopoietic, immunosuppressive, otologic, and renal, with the last two generally the most serious. Serial audiometry testing can generally warn of the otologic toxicity and thus prevent permanent acoustic damage. Renal toxicity, which is similar to that seen with heavy-metal poisoning, appears to be dose related, cumulative, and only partly reversible, thus, severely limiting the repeated administration of cis-dichlorodiammineplatinum (II). Recent laboratory studies suggest that combination chemotherapy with this drug may be rewarding. Studies of this nature should be pursued along with attempts to find more effective less toxic platinum compounds.

Antineoplastic Agents↗

Chiroptical switches and sensors based on ligand conformational changes in labile coordination complexes.

A series of molecules have been developed that give significantly differentiated circular dichroic signals upon presentation of a metal ion, exchange of metal ion, or change in oxidation state. These properties have led to prototypes of molecular sensors for metal ions and redox-mediated chiroptical switches. In some complexes, the CD signal arises by an excitonic coupling mechanism, affording further information about ligand conformation or absolute configuration.

Circular Dichroism↗