Self-assembly
of the selenium-bridged novel metallacyclophanes [{(CO)3Re(μ-SeR)2Re(CO)3}2(μ-L)2] (1–3) has been accomplished
by treating diaryl diselenide with low-valent transition-metal carbonyl
and rigid bidentate azine ligands under one-pot reaction conditions.
The oxidative addition of diphenyl/dibenzyl diselenides to Re2(CO)10 with 4,4′-bipyridine, trans-1,2-bis(4-pyridyl)ethylene, and 1,4-bis[2-(4-pyridyl)ethenyl]benzene
afforded tetranuclear metallacyclophanes. These compounds have been
characterized by elemental analysis and IR, NMR, and UV–vis
absorption spectroscopic techniques. The molecular structures of metallacylophanes 1a,b and 2 were determined by single-crystal
X-ray diffraction methods, and the crystal structures showed that
two selenium-bridged dirhenium metallacycles were linked by two bipyridyl
spacers and attained a framework of molecular rectangles. In addition,
the molecular recognition capabilities of the molecular rectangles 1a,b and 2 with aromatic compounds
such as pyrene and triphenylene have been investigated by studying
their binding properties, using UV–visible absorption and fluorescence
emission spectrophotometric methods. The nature of the binding interactions
were further supported by single-crystal X-ray diffraction methods,
and the crystal structures of 1
b·(pyrene)
and 1
b·(triphenylene) revealed that
CH···π interactions are mainly responsible for
the binding of 1b with pyrene and triphenylene.
Functionalized pyridyl ditopic ligands 1,2‐phenylene diisonicotinate (pdi) (L1) and N,N′‐4‐pyridylcarboxamide‐4‐pyridylcarboxyl‐1,2‐benzene (pcpcb) (L2) comprising ester/ester and amide backbone have been synthesized and utilized for the preparation of novel series of chalcogenolato‐bridged rhenium(I) metallacycles [(CO)3Re(μ‐ER)2Re(CO)3(μ‐pdi)] (1–4) and [(CO)3Re(μ‐ER)2Re(CO)3(μ‐pcpcb)] (5–8) (E=S, Se and Te; R=butyl and phenyl). Synthesis of metallacycles 1‐8 has been accomplished by the oxidative addition of dialkyl/diaryl dichalcogenide to rhenium carbonyl with ester/ester and amide functionalized pyridyl ditopic ligand in one‐pot reaction. The pyridyl ligands and metallacycles were characterized by elemental analysis, IR, NMR and UV‐Vis absorption spectroscopic techniques. Molecular structure of the metallacycles 2–4 and 7 were determined by single‐crystal X‐ray diffraction methods. Preliminary cytotoxic activities of the ligands and metallacycles were studied on various cancer and normal cells. The results revealed that the metallacycles selectively inhibited certain cancer cells but not the normal cells.
In perhaps the first-ever study of its kind, the effect of vermicompost, derived solely from an allelopathic weed, on the germination, growth, and yield of a botanical species, has been carried out. In test plots, the soil was treated with the vermicompost of lantana (Lantana camara) at the rates of 5, 7.5, and 10 t ha(-1), and cluster bean (Cyamopsis tetragonoloba) was grown on it. The performance of these systems was compared with the systems in which the soil was fortified with inorganic fertilizers (IFs) in concentrations equivalent to those present in the respective vermicompost (VC) treatments. Additionally, a set of control was studied in which the soil was used without fortification by either VC or IF. It was seen that up to 51.5 % greater germination success occurred in the VC treatments compared to controls. VC also supported better plant growth in terms of stem diameter, shoot length, shoot mass, number of leaves, and leaf pigments. The positive impact extended up to fruit yield. In addition, vermicast application enhanced root nodule formation, reduced disease incidence, and allowed for a smaller number of stunted plants. The results indicate that allelopathic ingredients of lantana seem to have been totally eliminated during the course of its vermicomposting and that lantana vermicompost has the potential to support germination, growth, and fruit yield better than equivalent quantities of IFs.
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