Studies on binuclear hydroxo/carboxylato-bridged manganese(III) complexes and a mononuclear manganese(III) complex involving salen type ligands

Synthesis of six hydroxo-bridged binuclear manganese(III) complexes of formulae [MnL-X-MnL](ClO₄) [X = OH (1–6)] along with a mononuclear manganese(III) complex (7) [Mn(L)(L′)(MeOH)₂] [HL′ = 2-(2-hydroxy-phen-yl)benzimidazole] and two carboxylate-bridged binuclear manganese(III) complexes (8) and (9) are described. The complexes have been characterized by the combination of i.r., u.v.-vis spectroscopy, magnetic moments and by their redox properties. The electronic spectra of all the complexes exhibit almost identical features consisting of two d–d bands at ca. 550 and 600 nm, one MLCT band at ca.400 nm, together with two π–π^* intra-ligand transitions at ca. 250 nm and ca.300 nm. Room temperature magnetic data range from μ = 2.7–3.0 BM indicates some super-exchange between the binuclear metal centers via bridging hydroxo/carboxylato groups. The X-ray crystal structure of the binuclear complex (5) revealed that it has a symmetric Mn^IIIN₂O₂ core bridged by a hydroxyl group. The X-ray analysis of the mononuclear complex (7) showed that the manganese-center possesses a distorted octahedral geometry. Electrochemical properties of hydroxo-bridged manganese(III) complexes (1–6) show identical features consisting of an irreversible and a quasi-reversible reduction corresponding to the Mn₂^III → Mn^IIMn^III → Mn^IIMn^II couples in the voltammogram. It was found that electron withdrawing substituents on the ligand result in easier reduction. Complex (7) displays an irreversible reduction at 0.08 V and a reversible oxidation at 0.45V assignable to the Mn^III → Mn^II reduction and Mn^III → Mn^IV oxidation, respectively. The carboxylate-bridged compound (8) exhibits two irreversible oxidations at 0.4 and 0.6 V, probably due to Mn₂^III → Mn^IIIMn^IV → Mn^IVMn^IV oxidations and shows a quasi-reversible reductive wave at −0.85 V, tentatively assigned to Mn₂^III → Mn^IIMn^III reduction.     

EOL and ETOL array languages

In this paper we study the families of ETOL and EOL array languages. Standard forms for ETOL and EOL array systems are defined and closure properties of the families are studied. Relations of these families with other developmental array languages and other array languages are studied.     

Total synthesis of (-)-anamarine

Total synthesis of polyhydroxy δ-pyranone natural product (-)-anamarine is accomplished from D-(-)-tartaric acid. The main feature of the synthesis is the utility of hitherto unexplored β-keto phosphonate derived from tartaric acid amide and further elaboration involving stereoselective reduction.     

Kinetics of the thallic ion oxidation of olefins

The kinetics of oxidation of chalkone (phenyl styryl ketone) and cinnamaldehyde by T1 (III) acetate in aqueous acetic acid is of the first order in olefin and first order with respect to the oxidant. The parameters of the transition state theory have been computed. The rate of the reaction is strongly accelerated by increasing acid concentration. The reaction rate is also retarded by added sodium chloride and sodium acetate. The results have been interpreted in the light of the ionic mechanism considering T1 (OAc)₃ to be the active oxidant in aqueous acetic acid.     

n-dimensional array languages and description of crystal symmetry—I

Following the general linguistic approach proposed by Narasimhan to pattern recognition we proposed two generative models,viz., the matrix models and the more powerful two-dimensional array models. In this paper we generalize the matrix models ton-dimensions and establish that then-dimensional matrix models are closed under union, concatenation, Kleene closure, ∈-free homomorphism, inverse homomorphism and intersection with regular matrices. Symmetry operations such as translation, reflection and half-turn are examined.     

Reaction of cis-Ru(bpy)2Cl2 with 1-phenyl 5-(aminophenyl) 9-(2-pyridyl) benzimidazole derivatives: crystal structures of N-(4-chlorophenyl) imidazo[1,5a] pyridine and cis-[Ru(bpy)2(MeCN)2](ClO4)2

Reaction of 1-phenyl 5-(aminophenyl) 9-(2-pyridyl) benzimidazole derivatives (2) with cis-Ru(bpy)₂Cl₂ in MeCN results in the formation of N-(aryl) imidazo[1,5a] pyridine derivatives (4) and cis-[Ru(bpy)₂(MeCN)₂]²⁺ (5). Crystal structures of N-(4-chlorophenyl) imidazo[1,5a] pyridine (4b) and cis-[Ru(bpy)₂(MeCN)₂](ClO₄)₂ (5) are also reported.     

Stereoselective synthesis of (−)-microcarpalide

A stereoselective approach for the synthesis of the bio-active decanolactone (−)-microcarpalide was achieved from chiral pool tartaric acid. The synthesis of pivotal intermediates en route to the decanolactone was achieved from α-benzyloxy aldehydes derived from l- and d-tartaric acid.     

Basic aspects and applications of tristimulus colorimetry

A detailed account of the specification of colour using the 1931 Commission International de L'Eclairage tristimulus coordinates and subsequent colour spaces for the measurement of small differences in colour is provided along with a review of the application of quantitative parameters for the evaluation of colour changes of acid-base and complexometric indicators. The development of screened indicators to improve the quality of colour changes at the equivalence point is discussed. Various computer programs proposed to calculate the different parameters by different algorithms are reviewed.