Structurally characterized luminescent lanthanide zinc carboxylate precursors for Ln-Zn-O nanomaterials

摘要

A novel family of lanthanide zinc carboxylate compounds was synthesized, characterized (structural determination and luminescent behavior), and investigated for utility as single-source precursors to Ln-Zn-O nanoparticles. Carboxylic acids [H-ORc = H-OPc (H-O_2CCH(CH_3)_2, H-OBc (H-O_2CC(CH_3)_3, H-ONc (H-O _2CCH_2C(CH_3)_3)] were individually reacted with diethyl zinc (ZnEt_2) to yield a set of previously unidentified zinc carboxylates: (i) [Zn(μ-ORc)_3Zn(μ-ORc)] _n [ORc = OPc (1), ONc (2)], (ii) [(py)Zn]_2(μ-ORc) _4 [ORc = OBc (3), ONc (4), and py = pyridine], or (iii) Zn(ORc) _2(solv)_2 [ORc/solv = OPc/py (5), O~cNc/H _2O (6) (O~cRc = chelating)]. Introduction of lanthanide cation [Ln[N(SiMe_3)_2]_3, ZnEt_2, and HOBc in py] yielded the mixed cationic species structurally characterized as: (i) (O~cBc)Ln[(μ-OBc)_3Zn(py)]_2 [Ln = Pr (7), Nd (8), Sm (9)] or (ii) (py)_2Zn(μ-OBc)_3Ln(O ~cBc)_2(py) [Ln = Tb (10), Dy (11), Er (12), Y (13), Yb (14)]. Exploration of alternative starting materials [Ln(NO_3) _3·nH_2O, Zn(O_2CCH_3) _2, HOBc in py] led to the isolation of (NO_3~c)Ln[(μ-OBc)_3Zn(py)]_2 [Ln = La (15), Ce (16), Pr (17), Nd (18), Sm (19), Eu (20), Gd (21), Tb (22) Dy (23), and Er (24); NO_3~c = chelating]. The UV-vis spectra of 7-24 revealed standard absorption spectra for the Ln cations. Representative compounds were used to generate nanoparticles from an established 1,4-butanediol-based solution precipitation route. The nanoproducts isolated adopted either a mixed zincite/lanthanum oxide (18n or 22n) or pure zincite (8n or 10n) phase dependent on NO_3 or OBc moiety. Fluorescence was not observed for any of these nanomaterials possibly due to phase separation, low crystallinity, surface traps, and/or quenching based on elevated Ln cation content.