Spectroscopic, structural, and thermodynamic aspects of the stereochemically active lone pair on lead(II): Structure of the lead(II) dota complex

摘要: Abstract Steric, thermodynamic, and spectroscopic consequences of a stereochemically active lone pair (Lp) in Pb(II) complexes are discussed. The structure Na3[Pb(dota)]NO3·2H2O (dota = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate) is reported: the four Pb–N bonds average 2.665 A, while Pb–O to acetate groups 2.772 A. Normally, M–N bond lengths longer than M–O lengths, as reported for Sr(II) dota complex. This reversal length order attributed being closer Lp on Pb(II). In line with latter, very long Pb⋯O contact 3.022 A found water molecule coordinated over proposed site Pb its Steric control whether active, that produces close 2.8 A length, can be exerted by ligands such cryptands prevent N donors ligand from coordinating together near opposite Lp, ‘antipodal’ site. intense band occurs electronic spectrum range 210–270 nm, 6s2 → 6sp transition, examined. shifts 209 nm Pb2+(aq) ion aqueous solution about 260 nm number increases series containing only O donors. Within this shift it same donors, there shorter wavelength, appears correlate change inactive active. DFT calculations support idea observed due transition filled 6s orbital an empty 6p orbital, suggest increasingly becomes hybridized more also interpretation wavelength