New N-nicotinyl and N-isonicotinyl, N′,N″-diaryl phosphorictriamides with new Er(III) complex: synthesis, spectroscopic study and crystal structures

Abstract

Ten new N-nicotinyl and N-isonicotinyl phosphoramidates with formula XP(O)R2, X = Nicotinamide(nia), R = NHCH2Ph (1), N(CH3)CH2Ph (2), NHCH(CH3)Ph (3), NH-CH2C4H3O (4), NHCH2(C5H4N) (5), 3-NH-C5H4N (6), and YP(O)R2, Y = isonicotinamide(iso), R = NHCH2Ph (7), N(CH3)CH2Ph (8), NHCH(CH3)Ph (9), NH-CH2C4H3O (10) plus one new Er(III) complex with formula Er(L)2(NO3)3 (11), L = (iso)PO(NHCH2C4H3O)2 (10), were synthesized and characterized by elemental analysis and 1H, 13C, 31P NMR, IR, UV–vis spectroscopy. Crystal structures of compounds 10 and 11 were also determined by X-ray crystallography. Interestingly, the 1H NMR spectra of compounds 1, 2, 6, 7, 9 indicated long-range n J P,H (n = 5,6,7) coupling constants, in the range of 1.4–1.9 Hz, for the splitting of pyridine ring protons with phosphorus atom. IR results showed that the ν(C=O) values of compounds 7–10 are greater than those of compounds 1–5 which means that isonicotinyl moiety is more electron withdrawing than nicotinyl group. X-ray outcomes revealed that in complex 11 three phosphoric triamide ligands have been connected to each Er(III); one from Npyridine and two from P=O donor sites. One of the P=O donor ligands is mono dentate while the other one acts as a bidentate ligand and coordinates to another Er atom via its Npyridine site. By forming complex 11 the P=O and C–Namide bond lengths of ligand is increased in both, mono and bi dentate, ligands while the C=O bond length is decreased to lower values. These variations are in good agreement with IR results. All H-bonds and electrostatic interactions lead to form a three-dimensional polymeric cluster in the crystal lattice of 10 and 11.