Electrochemistry of different types of photoreactive ruthenium(II) dicarbonyl α-diimine complexes

The photochemical reactivity, photophysical properties and redox behavior of the complexes trans,cis-[Ru(X)(X′)(CO)₂(α-diimine)] and their derivatives are strongly dependent on the complex geometry, the nature and electronic properties of the α-diimine ligand and, most importantly, on the axial ligands X and X′ (alkyl, halide, phosphine, donor solvent, etc.). This paper deals mainly with comparison of reduction pathways for several different types of the trans,cis-[Ru(X)(X′)(CO)₂(α-diimine)] complexes, also presenting some new results in this field. An equally important goal has been the comparison and discussion of the photo- and redox reactivity of these complexes from the viewpoint of the frontier orbitals involved and character of the Ru---X/X′ bonding.     

C-Glucosylflavonoid biosynthesis from 2-hydroxynaringenin by Desmodium uncinatum (Jacq.) (Fabaceae)

[2′,3′,5′,6′-²H₄]-2-Hydroxynaringenin is synthesised and incubated with commercially available UDP-glucose and the crude protein extract from Desmoduim uncinatum leaves. The organic extract produces isotopically labelled [2′,3′,5′,6′-²H₄]-vitexin and [2′,3′,5′,6′-²H₄]-isovitexin. Repeating the experiment with denatured protein or replacing the 2-hydroxynaringenin with [2′,3′,5′,6′-²H₄]-apigenin or [2′,3′,5′,6′-²H₄]-naringenin results in no observable incorporation. 2-Hydroxynaringenin is therefore the substrate for C-glucosylflavonoid biosynthesis in D. uncinatum.     

New approaches to synthesis of tris[1,2,4]triazolo[1,3,5]triazines

Thermal cyclization of 3-R-5-chloro-1,2,4-triazoles (R = Cl, Ph) afforded 2,6,10-tri-R- tris[1,2,4]triazolo[1,5-a:1′,5′c:1″,5″-e][1,3,5]triazines 5 (R = Ph) and 7 (R = Cl). These compounds are first representatives of this class of heterocycles, whose structures were unambiguously established. Treatment of these compounds with nucleophiles (H₂O/NaOH, NH₃) results in the triazine ring opening to give compounds consisting of three 1,2,4-triazole rings linked in a chain. For example, treatment of cyclic compound 5 with aqueous alkali affords 3-phenyl-1-3-phenyl-1-(3-phenyl-1H-1,2,4-triazol-5-yl)-1,2,4-triazol-5-yl-1H-1,2,4-triazol-5-one. Treatment of 3,7,11-triphenyltris[1,2,4]triazolo[4,3-a:4′,3′c:4″,3″-e][1,3,5]triazine (2) with HCl/SbCl₅ leads to the triazine ring opening giving rise to 5-(3-chloro-5-phenyl-1,2,4-triazol-4-yl)-3-phenyl-4-(5-phenyl-1H-1,2,4-triazol-3-yl)-1,2,4-triazole. Thermal cyclization of the latter produces 3,7,10-triphenyltris[1,2,4]triazolo[1,5-a:4′,3′c:4″,3″-e][1,3,5]triazine (13). Thermolysis of both cyclic compound 2 and cyclic compound 13 is accompanied by the Dimroth rearrangement to yield 3,6,10-triphenyl-tris[1,2,4]triazolo[1,5-a:1′, 5′-c:4″,3″-e][1,3,5]triazine (14). Compounds 13 and 14 are the first representatives of cyclic compounds with this skeleton. ¹³C NMR spectroscopy allows the determination of the isomer type in a series of tris[1,2,4]triazolo[1,3,5]triazines.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 706–712, March, 2005.     

Synthesis, characterization and photophysics of bimetallic manganese(I) and ruthenium(II) complexes

A series of new manganese(I) and ruthenium(II) monometallic and bimetallic complexes made of 2,2′-bipyridine and 1,10-phenanthroline ligands, [Mn(CO)₃(NN)(4,4′-bpy)]⁺, [{(CO)₃(NN)Mn}₂(4,4′-bpy)]²⁺ and [(CO)₃(NN)Mn(4,4′-bpy)Ru(NN)₂Cl]²⁺ (NN = 2,2′-bipyridine, 1,10-phenanthroline; 4,4′-bpy = 4,4′-bipyridine) are synthesized and characterized, in addition to already known ruthenium(II) complexes [Ru(NN)₂Cl(4,4′-bpy)]⁺ and [Cl(NN)₂Ru(4,4′-bpy)Ru(NN)₂Cl]²⁺. The electrochemical properties show that there is a weak interaction between two metal centers in Mn–Ru heterobimetallic complexes. The photophysical behavior of all the complexes is studied. The Mn(I) monometallic and homobimetallic complexes have no detectable emission. In Mn–Ru heterobimetallic complexes, the attachment of Mn(I) with Ru(II) provides interesting photophysical properties.     

Structure-Property Relationship in Bispyrrolizidine Photochromic Compounds Derived from Indolo[4,5-<Emphasis Type="Italic">e</Emphasis>]- and -[7,6-<Emphasis Type="Italic">g</Emphasis>]indoles

The spirocyclic compounds bis[2′,3′-bis(methoxycarbonyl)-5′,6′,6′ -trimethylspirofluoren-9,4′-(1′-aza-2′-cyclopentene)][1′,5′ -a]indolino[4,5-e]indoline and bis[2-,3′-bis(methoxycarbonyl)-5′,6′,6′ -trimethylspiro-fluoren-9,4′-(1′-aza-2′-cyclopentene)][1′,5′ -a]indolino[7,6-g]indoline exhibit photochromic properties with various half-lifes. The AM1 method was used to correlate the structural and electronic properties, on the one hand, and photochromic properties, on the other, and to explain reasons for the difference in the photochromism of the two compounds.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 4, 2005, pp. 670–673.Original Russian Text Copyright © 2005 by Samsoniya, Trapaidze, Tsikoliya, Machaidze, Esakiya.     

Specific Features of Reaction of 2-R-Benzo[e][1,3,2]dioxaphosphinin-4-ones with Perfluorodiacetyl. Synthesis and Steric Structure of 4′,5′-Bis(trifluoromethyl)-4-oxo-2-(2,2,3,3-tetrafluoropropoxy)-2λ 5-spiro[benzo[e][1,3,2]dioxaphosphinine-2,2′-[1,3,2]dioxaphosphole]

2-R-benzo[e][1,3,2]dioxaphosphinin-4-ones react with perfluorodiacetyl under mild conditions to form relatively labile spirophosphoranes containing a 1,3,2-dioxaphosphole ring. These compounds gradually convert to more stable 2-R-4,5-bis(trifluoromethyl)-1,3,2λ⁵-dioxaphosphole 2-oxides and diastereometic 2-R-4-(trifluoroacetyl)-4-(trifluoromethyl)benzo[f][1,3,2λ⁵]dioxaphosphepine 2-oxides, whose structure was confirmed by means of NMR and IR spectroscopy. The structure of 4′,5′ -bis(trifluoromethyl)-4-oxo-2-(2,2,3,3-tetrafluoropropoxy)-2λ ⁵-spiro[benzo[e][1,3,2]dioxaphosphinine-2,2′-[1,3,2]dioxaphosphole] was confirmed by X-ray diffraction analysis.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 4, 2005, pp. 587–599.Original Russian Text Copyright © 2005 by Konovalova, Mironov, Ivkova, Zagidullina, Gubaidullin, Litvinov, Kurykin.     

Triplet level-dependent photoluminescence and photoconduction properties of π-conjugated polymer thin films doped by iridium complexes

Triplet energy level-dependent decay pathways of excitons populated on iridium (Ir) complexes within π-conjugated polymeric matrices were studied by means of photoluminescence (PL) and photoconduction action spectroscopy. We chose a set of matrices, poly(9-vinylcarbazole) (PVK), poly[9,9-bis(2-ethylhexyl)fluorene-2,7-diyl] (PF2/6), poly [2-(5′-cyano-5′-methyl-hexyloxy)-1,4-phenylene] (CNPPP), and poly [2-(5′-cyano-5′-methyl-hexyloxy)-1,4-phenylene-co-pridine] (CNPPP-py10 and CNPPP-Py20), having triplet energy levels ranging from 2.2 up to 3.0 eV. As Ir-complex dopants, we selected three phosphorescent emitters, iridium(III)bis(2-(2′-benzothienyl) pyridinato-N-acetylacetonate) (Ir(btp)₂acac), iridium(III)fac-tris(2-phenylpyridine) (Ir(ppy)₃), and iridium(III)bis[(4,6-fluorophenyl)-pyridinato-N,C^2′]picolinate (FIrpic), having triplet energy levels of 2.1, 2.5, and 2.7 eV, respectively. It was found that the triplet emission from the dopants, being populated via energy transfer from the matrices, was strongly dependent on the matching of triplet energy levels between matrix polymers and Ir-complexes. Photocurrent action spectra confirm effective exciton confinement at the dopants sites in the case of PVK matrix systems.     

Synthesis, reactions and X-ray crystal structures of metallacrown ethers with unsymmetrical bis(phosphinite) and bis(phosphite) ligands derived from 2-hydroxy-2′-(1,4-bisoxo-6-hexanol)-1,1′-biphenyl

Chlorodiphenylphosphine and 2,2′-biphenylylenephosphorochloridite react with 2-hydroxy-2′-(1,4-bisoxo-6-hexanol)-1,1′-biphenyl to yield the new α,ω-bis(phosphorus-donor)-polyether ligands, 2-Ph₂PO(CH₂CH₂O)₂–C₁₂H₈-2′-OPPh₂ (1) and 2-(2,2′-O₂C₁₂H₈)P(CH₂CH₂O)₂–C₁₂H₈-2′-P(2,2′-O₂C₁₂H₈) (2). These ligands react with Mo(CO)₄(nbd) to form the monomeric metallacrown ethers, cis-Mo(CO)₄{2-Ph₂PO(CH₂CH₂O)₂–C₁₂H₈-2′-OPPh₂} (cis-3) and cis-Mo(CO)₄{2-(2,2′-O₂C₁₂H₈)P(CH₂CH₂O)₂–C₁₂H₈-2′-P(2,2′-O₂C₁₂H₈)} (cis-4), in good yields. The X-ray crystal structures of cis-3 and cis-4 are significantly different, especially in the conformation of the metal center and the adjacent ethylene group. The very different ¹³C-NMR coordination chemical shifts of this ethylene group in cis-3 and cis-4 suggest that the solution conformations of these metallacrown ethers are also quite different. Both metallacrown ethers undergo cis–trans isomerization in the presence of HgCl₂. Although the cis–trans equilibrium constants for the isomerization reactions are nearly identical, the isomerization of cis-3 is more rapid. Phenyl lithium reacts with cis-3 to form the corresponding benzoyl complexes but does not react with either trans-3 or cis-4. Both the slower rate of cis–trans isomerization of cis-4 and its lack of reaction with PhLi are consistent with weaker interactions between the hard metal cations and the carbonyl oxygens in both trans-3 and cis-4.     

Heterobimetallic platinum–copper and platinum–silver transition metal complexes based on cis-[Pt](CCPh)2: an overview

The reaction of cis-[Pt](CCPh)₂ {[Pt]=(bipy)Pt, (bipy′)Pt; BIPY=2,2′-bipyridine, bipy′=4,4′-dimethyl-2,2′-bipyridine} with different copper(I) and silver(I) salts [M′X] (M′=Cu, Ag; X=inorganic or organic ligand) produces alkynyl-bridged (hetero)bi-, tri-, tetra- or pentametallic transition metal complexes. The structural aspects and reaction chemistry of such species and the preference for one coordination mode over another is discussed. The interconversion and mechanistical aspects in the formation of the latter complexes is also reported.     

Reactions of Substituted Ethyl 1,2,3,4,4′,5′-Hexahydrospiro-[naphthalene-2,5′-pyrazole]-3′-carboxylates with Halogens

Substituted ethyl 1,2,3,4,4′,5′-hexahydrospiro[naphthalene-2,5′-pyrazole]-3′-carboxylates react with chlorine or N-bromosuccinimide to give spirocyclic substituted 3-halo-4,5-dihydro-3H-pyrazoles which lose nitrogen molecule on heating with formation of substituted spirocyclic 1-halocyclopropane-1-carboxylates. Heating of the title compounds with bromine in acetic acid results in opening of the spiro-fused six-membered ring to afford ethyl 4-aryl-5-[2-(2-carboxyphenyl)ethyl]pyrazole-3-carboxylates.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 7, 2005, pp. 1058–1063.Original Russian Text Copyright © 2005 by Molchanov, Korotkov, Kopf, Kostikov.     

Unusual case of catalysis by palladium clusters

An unusual for Pd catalysts dehydration of α-alkyl and α, α′-dialkylbenzyl alcohols PhCR′R″OH (R′ = H, Me, Et, Bu; R″ = H, Me) occurs in the presence of the palladium(I) cluster [Pd₄(CO)₄(OAc)₄] (1) in an inert atmosphere to form ethers PhCR′R″-O-CR′ R″ and water. The catalyst is an intermediate of cluster 1 reduction to Pd black, while neither the starting cluster 1, nor Pd black, which is the decomposition product, are active in the catalysis of this reaction.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 788–791, March, 2005.     

Synthesis and characterization of novel α- or β-tetra[6,7-dihexyloxy-3-(4-oxyphenyl)coumarin]-substituted metal-free and metallo phthalocyanines

The synthesis of novel phthalonitriles substituted at 3- or 4-position with 6,7-dihexyloxy-3-(4-oxyphenyl)coumarin were performed. The metal-free and metallo phthalocyanines (MPcs) (M = Zn, Co, Cu) were prepared by cyclotetramerization of 6,7-dihexyloxy-3-[p-(2′,3′-dicyanophenoxy)phenyl]coumarin or 6,7-dihexyloxy-3-[p-(3′,4′-dicyanophenoxy)phenyl]coumarin. The newly prepared compounds, phthalonitriles and Pcs, have been characterized by elemental analysis, ¹H NMR, ¹³C NMR, MALDI-TOF, IR, UV–Vis and fluorescence spectral data. The electronic spectra exhibit bands of coumarin identity along with characteristic Q and B bands of the Pc core. The IR-spectra of all Pcs showed three characteristic intense bands at 1709–1700 cm⁻¹ for lactone carbonyl, two bands at 1489–1604 cm⁻¹ for conjugated olefinic system.     

Synthesis, characterization and physicochemical studies of weakly interacting redox-responsive binuclear complexes incorporating ethylenediaminetetraacetatoruthanate(III)

Novel binuclear complexes of the type [{Ru(edtaH)}₂L] [edta- = ethylenediaminetetraacetate, L = pyrazine, 4,4′-bipyridyl, 3,3′-dimethyl-4,4′-bipyridyl, trans-1,2-bis(4-pyridyl)ethylene)] have been synthesized and characterized by physicochemical methods. All the complexes showed weak metal-metal interaction, depending on the nature of the bridging ligand, L. The electrochemical and magnetic susceptibility measurements are consistent with weak interactions between the ruthenium centres.     

Biphenyl- and terphenyl-based recyclable organic trivalent iodine reagents

Biphenyl- and terphenyl-based recyclable trivalent iodine reagents, such as 4-bromo-4′-(diacetoxyiodo)biphenyl, 4,4′-bis(diacetoxyiodo)biphenyl, 1,4-bis[4-(diacetoxyiodo)phenyl]benzene, 4-bromo-4′-[(hydroxy)(tosyloxy)iodo]biphenyl, 4,4′-bis[(hydroxy)(tosyloxy)iodo]biphenyl, were simply prepared and their reactivities for the oxidative rearrangement of ketones to esters, TEMPO-mediated oxidation of alcohols to aldehydes or ketones, oxidative dealkylation of N-alkylsulfonamides to sulfonamides, and α-tosyloxylation of ketones were compared with p-(diacetoxyiodo)toluene and p-[(hydroxy)(tosyloxy)iodo]toluene to show the same reactivities and, moreover, the biphenyl- and terphenyl-based iodoarenes formed were recovered by simple filtration of the reaction mixture in every reaction. Thus, these biphenyl- and terphenyl-based trivalent iodine reagents can be used as the recyclable reagents.     

Synthesis and molecular structure of cisoid and transoid isomers of [Re2(CO)6(1,1′-bis(indenylidene)] derived from the reaction of [Re2(CO)8(MeCN)2] and diazoindene

The compound [Re₂(CO)₈(MeCN)₂] reacts with diazoindene (C₉H₆N₂) while refluxing in THF to afford three dirhenium products in which C₉H₆N₂ is cleaved with loss of N₂ and with incorporation of the residual indenylidene group into the products. Two indenylidene groups are coupled in two diastereomers of [Re₂(CO)₆(μ,η⁵:η⁵-1,1′-C₁₈H₁₂)] where C₁₈H₁₂=bis(indenylidene). X-ray structures show that these isomers are related as RR/SS and RS isomers. These have the two Re(CO)₃ groups coordinated transoid and cisoid, respectively to a trans bis(indenylidene) bridge. The third product is the μ-indenylidene complex [Re₂(CO)₈(μ,η¹:η⁵-C₉H₆)], which was also structurally characterised by X-ray diffraction.     

2-Nitroguanidine Derivatives: IX. Reaction of 1-Amino-2-nitroguanidine with Oxalic Acid as a Method of Synthesis of 3(5)-Nitroamino-1,2,4-triazole-5(3)-carboxylic Acid and 5,5′-Bi(3-nitroamino-1,2,4-triazole) Salts

A new procedure for the synthesis of 5(3)-nitroamino-1,2,4-triazole-3(5)-carboxylic acid and 5,5′ -bi(3-nitroamino-1,2,4-triazole) potassium salt has been developed. It includes cyclization of [2-(N²-nitro-carbamimidoyl) hydrazino]oxoacetic acid and 2,2′-bis(N ²-itrocarbamimidoyl)oxalohydrazide, respectively, which are prepared by reaction of 1-amino-2-nitroguanidine with oxalic acid. The reaction of 5(3)-nitroamino-1,2,4-triazole-3(5)-carbohydrazide with 1-methyl-2-nitro-1-nitrosoguanidine leads to N′ -(N ²-nitrocarbamimidoyl)-5(3)-nitroamino-1,2,4-triazole-3(5)-carbohydrazide whose intramolecular cyclization in the presence of bases may be regarded as a new method of synthesis of 5,5′-bi(3-nitroamino-1,2,4-triazole) salts.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 3, 2005, pp. 447–450.Original Russian Text Copyright © 2005 by Metelkina, Novikova, Berdonosova, Berdonosov.For communication VIII, see [1].     

Aluminum complexes of sterically hindered tetradentate Schiff bases: Synthesis, structure, and reactivity toward -caprolactone

The sterically hindered Schiff bases tbmSalenH₂ [tbmSalen = N,N′-1,2-ethylenebis(3-tert-butyl-5-methylsalicylideneimine)] and tbmSalcenH₂ [tbmSalcen = N,N′-trans-1,2-cyclohexanediyl-bis(3-tert-butyl-5-methylsalicylideneimine)] afforded a series of aluminum complexes of the general formulae [Al(tbmSalen)X] and [Al(tbmSalcen)X] (X = Cl, Me, Et). The molecular structure of [Al(tbmSalcen)Cl] was determined by single-crystal X-ray structural analysis which revealed a five-coordinate aluminum center with a distorted square pyramidal geometry. The alkyl complexes were found to oligomerize -caprolactone.     

Synthesis and reactivity of neodymium(III) amido-tethered N-heterocyclic carbene complexes

The reaction of the heteroleptic Nd(III) iodide, [Nd(L′)(N″)(μ-I)] with the potassium salts of primary aryl amides [KN(H)Ar′] or [KN(H)Ar^*] affords heteroleptic, structurally characterised, low-coordinate neodymium amides [Nd(L′)(N″)(N(H)Ar′)] and [Nd(L′)(N″)(N(H)Ar^*)] cleanly (L′ = t-BuNCH₂CH₂[C{NC(SiMe₃)CHNt-Bu}], N″ = N(SiMe₃)₂, Ar′ = 2,6-Dipp₂C₆H₃, Dipp = 2,6-Prⁱ₂C₆H₃, Ar^* = 2,6-(2,4,6-Prⁱ₃C₆H₂)₂C₆H₃). The potassium terphenyl primary amide [KN(H)Ar^*] is readily prepared and isolated, and structurally characterised. Treatment of these primary amide-containing compounds with alkali metal alkyl salts results in ligand exchange to give alkali metal primary amides and intractable heteroleptic Nd(III) alkyl compounds of the form [Nd(L′)(N″)(R)] (R = CH₂SiMe₃, Me). Attempted deprotonation of the Nd-bound primary amide in [Nd(L′)(N″)(N(H)Ar^*)] with the less nucleophilic phosphazene superbase Bu^tNP{NP(NMe₂)₃}₃ resulted in indiscriminate deprotonations of peripheral ligand CH groups.