Turning a "useless" ligand into a "useful" ligand:a magneto-structural study of an unusual family of Cu(II) wheels derived from functionalised phenolic oximes

While the phenolic oximes (R-saoH(2)) are well known for producing monometallic complexes of the type [MII(R-saoH)(2)] with Cu-II ions in near quantitative yield, their derivatisation opens the door to much more varied and interesting coordination chemistry. Here we show that combining the complimentary diethanolamine and phenolic oxime moieties into one organic framework (H4L1 and H4L2) allows for the preparation and isolation of an unusual family of [Cu-II](n) wheels, including saddle-shaped, single-stranded [Cu-8(II)] wheels of general formula [Cu-8(HL1)(4)(X)(4)] n[Y] (when n = 0, X = Cl-, NO3-, AcO-, N-3(-); when n = 2+X = (OAc)(2)/(2,2'-bpy)(2) and Y = [BF4](2)) and [Cu-8(HL2)(4)(X)(4)](X = Cl-, Br-), a rectangular [Cu-6(HL1)(4)] wheel, and a heterometallic [Cu4Na2(HL1)2(H2L1)(2)] hexagon. Magnetic studies show very strong antiferromagnetic exchange between neighbouring metal ions, leading to diamagnetic ground states in all cases. DFT studies reveal that the magnitude of the exchange constants are correlated to the Cu-N-O-Cu dihedral angles, which in turn are correlated to the planarity/puckering of the [Cu-II](n) rings

Study of Large & Medium Scale Irregularities Using 140 MHz ATS-6 Faraday Rotation Records from Three Stations

245-249The drift velocities of medium and large scale irregularities have been estimated utilizing the 140 MHz ATS-6 Faraday rotation records obtained simultaneously at Delhi, Kurukshetra and Pilani. The triangulation method of determining the velocities in a general case has been described. The drift velocities of these irregularities have been found to vary from 30 to about 500 m/sec, the commonest speed being about 140 m/sec during the day and about 110 m/sec during the night. These velocities are found to be spread in all possible directions except that during daytime no irregularity was found to be moving in south-east direction while during nighttime only one irregularity was found to be moving in north-east direction. Both periodic and non-periodic TIDs have been observed but most of the disturbances belong to medium scale rather than to large scale TIDs