Search results for "Intramolecular force"
showing 10 items of 599 documents
Synthesis and structures of some diorganotin bis(hydroxamate)s
1994
Analysis of literature data on the antitumor activity of organotin compounds reveals that R2SnX2 and their complexes containing SnO, SnN or SnS bonds often exhibit biological activity, especially if such bonds are formed by means of intramolecular coordination. Furthermore, a wide range of biological activities, from fungicidal, bactericidal and antiseptic to psychotropic and antitumor, is found to be characteristic for some organic hydroxamic acids (N-acylhydroxylamines). From this point of view the diorgantion bis-hydroxamates in this paper are of particular interest as potential biologically active antitumor drugs. Di-n-butyltin bis(N-methyl-N-p-bromobenzoylhydroxylamine) is being screen…
Syntheses, Crystal Structures, and Magnetic Properties of the Oxalato-Bridged Mixed-Valence Complexes [FeII(bpm)3]2[FeIII2(ox)5]·8H2O and FeII(bpm)3N…
2001
The preparation and crystal structures of two oxalato-bridged FeII-FeIII mixed-valence compounds, [FeII(bpm)3]2[FeIII2(ox)5].8H2O (1) and FeII(bpm)3Na(H2O)2FeIII(ox)(3).4H2O (2) (bpm = 2,2'-bipyrimidine; ox = oxalate dianion) are reported here. Complex 1 crystallizes in the triclinic system, space group P1, with a = 10.998(2) A, b = 13.073(3) A, c = 13.308(3) A, alpha = 101.95(2) degrees, beta = 109.20(2) degrees, gamma = 99.89(2) degrees, and Z = 1. Complex 2 crystallizes in the monoclinic system, space group P2(1)/c, with a = 12.609(2) A, b = 19.670(5) A, c = 15.843(3) A, beta = 99.46(1) degrees, and Z = 4. The structure of complex 1 consists of centrosymmetric oxalato-bridged dinuclear h…
Magneto-structural studies on heterobimetallic malonate-bridged M(II)Re(IV) complexes (M = Mn, Co, Ni and Cu).
2010
The mononuclear Re(IV) compound of formula (PPh(4))(2)[ReBr(4)(mal)] (1) was used as a ligand to obtain the heterobimetallic species [ReBr(4)(μ-mal)Co(dmphen)(2)]· MeCN (2), [ReBr(4)(μ-mal)Ni(dmphen)(2)] (3), [ReBr(4)(μ-mal)Mn(dmphen)(2)] (4a), [ReBr(4)(μ-mal)Mn(dmphen)(H(2)O)(2)]·dmphen·MeCN·H(2)O (4b), [ReBr(4)(μ-mal)Cu(phen)(2)]·1/4H(2)O (5) and [ReBr(4)(μ-mal)Cu(bipy)(2)] (6) (mal = malonate dianion, dmphen = 2,9-dimethyl-1,10-phenanthroline, phen = 1,10-phenanthroline and bipy = 2,2'-bipyridine). The structures of 2 and 5 (single-crystal X-ray diffraction) are made up of neutral [ReBr(4)(μ-mal)M(AA)] dinuclear units [AA = dmphen with M = Co (2) and AA = phen with M = Cu (5)] where the …
N-methyl-1,2-dihydro-2-benzoylmethylenequinolines: configurational dissimilarity with unmethylated congeners
2000
Abstract Twelve 1-methyl-1,2-dihydro-2-benzoylmethylenequinolines have been synthesized and their structures elucidated by 1 H, 13 C and 15 N NMR, UV–Vis and X-ray methods. The results unambiguously show that these compounds and the corresponding 1,2-dihydro-2-benzoylmethylenequinolines both in crystalline and in solution state are the Z and E isomers, respectively. Comparison of the X-ray structures reveal that ( Z )-1,2-dihydro-2-benzoyl-methylenequinolines are less twisted as compared to their 1-methyl derivatives. This difference is caused by formation of the quasi-aromatic six-membered ring stabilized by an intramolecular hydrogen bond in unmethylated congeners, prevented by N -methyla…
Synthesis, Structural, Thermal and Magnetic Characterization of a Pyrophosphato‐Bridged Cobalt(II) Complex
2008
The reaction in water of CoII sulfate heptahydrate with 1,10-phenanthroline (phen) and sodium pyrophosphate (Na4P2O7) in a 2:4:1 stoichiometric ratio resulted in the crystallization of a neutral dinuclear CoII complex, {[Co(phen)2]2(μ-P2O7)}·6MeOH (1), as revealed by a single-crystal X-ray diffraction study. The bridging pyrophosphato ligand between the two [Co(phen)2]2+ units in a bis(bidentate) coordination mode places the adjacent metal centers at 4.857 A distance, and its conformation gives rise to intramolecular π–π stacking interaction between adjacent phen ligands. Indeed, intermolecular π–π stacking interactions between phen ligands from adjacent dinuclear complexes create a supramo…
Synthesis, crystal structures and magnetic properties of cyanide- and phenolate-bridged [MIIINiII]2tetranuclear complexes (M = Fe and Cr)
2005
The binuclear complex NiII2L(H2O)2(ClO4)2 (1) and the neutral tetranuclear bimetallic compounds [{MIII(phen)(CN)4}2{NiII2L(H2O)2}]·2CH3CN with M = Fe (2) and Cr (3) [H2L = 11,23-dimethyl-3,7,15,19-tetraazatricyclo[19.3.1.19,13]hexacosa-2,7,9,11,13(26),14,19,21(25),22,24-decaene-25,26-diol] have been synthesized and the structures of 2 and 3 determined by single crystal X-ray diffraction. 2 and 3 are isostructural compounds whose structure is made up of centrosymmetric binuclear cations [Ni2(L)(H2O)2]2+ and two peripheral [M(phen)(CN)4]− anions [M = Fe (2) and Cr (3)] acting as monodentate ligands towards the nickel atoms through one of their four cyanide nitrogen atoms. The environment of t…
A Novel Dinuclear Fe II Spin‐Crossover Complex Based on a 2,2‐Bipyrimidine Bridge Ligand: [Fe(CH 3 bipy)(NCS) 2 ] 2 bpym
2004
The dinuclear iron(II) complex {[Fe(CH3bipy)(NCS)2]2bpym} has been synthesised and its crystal structure determined at 293 K. The magnetic properties display intramolecular antiferromagnetic coupling at 1 bar (J = −4.2 cm−1), and the onset of a pressure-induced spin conversion is observed at 11 kbar. Magnetic field Mossbauer measurements have been carried out at 4.2 K, and indicate that the HS species correspond to [HS-HS] pairs. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Magnetic properties and molecular structures of binuclear (2-pyrazinecarboxylate)-bridged complexes containing Re(iv) and M(ii) (M = Co, Ni)
2007
Three novel Re(iv) compounds, the mononuclear complex Bu(4)N[ReBr(5)(Hpyzc)] (1) and the heterobimetallic complexes [ReBr(5)(mu-pyzc)M(dmphen)(2)].2CH(3)CN [M = Co (2), Ni (3)] (Hpyzc = 2-pyrazinecarboxylic acid, dmphen = 2,9-dimethyl-1,10-phenanthroline), have been synthesized and their crystal structures determined by single-crystal X-ray diffraction. The structure of 1 consists of [ReBr(5)(Hpyzc)](-) complex anions and tetrabutylammonium cations, Bu(4)N(+). The Re(iv) is surrounded by five bromide anions and a N-donor Hpyzc monodentate ligand, in a distorted octahedral environment. The structures of 2 and 3 consist of dinuclear units [ReBr(5)(mu-pyzc)M(dmphen)(2)], with the metal ions li…
Exploring the Role of Intramolecular Interactions in the Suppression of Quantum Tunneling of the Magnetization in a 3d-4f Single-Molecule Magnet.
2021
Hydroxide-bridged FeIII4LnIII2 clusters having the general formula [Fe4Ln2(μ3-OH)2(mdea)6(SCN)2(NO3)2(H2O)2]·4H2O·2MeCN {Ln = Y (1), Dy (2), mdea = N-methyldiethanolamine} were synthesized and magnetically characterized. The thermal relaxation of the magnetization for 2 and the diluted FeIII4DyIIIYIII complex 3 (with and without applied field) has been analyzed. The diluted sample shows a dominant QTM at low temperatures that can be removed with a 0.15 T dc field. Both 2 and 3 show moderately high Ueff barriers and exhibit hysteresis loops until 5 K.
Kinetische Untersuchungen zur Bildung der E ‐ und Z ‐Enole bei der Thermolyse von 2‐Diazo‐1,3‐dimesityl‐1,3‐propandion in Nucleophilen
1988
Bei der Thermolyse der Diazoverbindung 1 in Ethanol bzw. Piperidin oder Morpholin entstehen die Enole 3a–c von β-Ketocarbonsaurederivaten. Z- und E-Konfigurationen stehen miteinander im Gleichgewicht. Die Bestimmung der Geschwindigkeits-konstanten zeigt, das sich zunachst bevorzugt die Z-Formen bilden; im Gleichgewicht dominieren jedoch schlieslich in den Thermolysemedien die E-Isomeren. In aprotischen, apolaren oder masig polaren Medien uberwiegen dagegen die Z-Isomeren mit einer intramolekularen Wasserstoffbrucke. Investigation on the Kinetics of the Formation of E- and Z-Enols in the Thermolysis of 2-Diazo-1,3-propanedione in Nucleophiles Thermolysis of the diazo compound 1 in ethanol an…