Synthesis, characterization, and electrochemical properties of a series of sterically varied iron(II) alkoxide precursors and their resultant nanoparticles.

A new family of iron(II) aryloxide [Fe(OAr)(2)(py)(x)] precursors was synthesized from the alcoholysis of iron(II) mesityl [Fe(Mes)(2)] in pyridine (py) using a series of sterically varied 2-alkyl phenols (alkyl = methyl (H-oMP), isopropyl (H-oPP), tert-butyl (H-oBP)) and 2,6-dialkyl phenols (alkyl = methyl (H-DMP), isopropyl (H-DIP), tert-butyl (H-DBP), phenyl (H-DPhP)). All of the products were found to be mononuclear and structurally characterized as [Fe(OAr)(2)(py)(x)] (x = 3 OAr = oMP (1), oPP (2), oBP (3), DMP (4), DIP (5); x = 2 OAr = DBP (6), DPhP (7)). The use of tris-tert-butoxysilanol (OSi(OBu(t))(3) = TOBS) led to isolation of [Fe(TOBS)(2)(py)(2)] (8). The new Fe(OAr)(2)(py)(x) (1-6) were found, under solvothermal conditions, to produce nanodots identified by PXRD as the γ-maghemite phase. The model precursor 3 and the nanoparticles 6n were evaluated using electrochemical methods. Cyclic voltammetry for 3 revealed multiple irreversible oxidation peaks, which have been tentatively attributed to the loss of alkoxide ligand coupled with the deposition of a solid Fe-containing coating on the electrode. This coating was stable out to the voltage limits for the acetonitrile solvent.

Series of comparable dinuclear group 4 neo-pentoxide precursors for production of pH dependent group 4 nanoceramic morphologies.

A series of similarly structured Group 4 alkoxides was used to explore the cation effect on the final ceramic nanomaterials generated under different pH solvothermal (SOLVO) conditions. The synthesis of [Ti(µ-ONep)(ONep)(3)](2) (1, ONep = OCH(2)C(CH(3))(3)) and {[H][(µ-ONep)(3)M(2)(ONep)(5)(OBu(t))]} where M = Zr (2) and Hf (3, OBu(t) = OC(CH(3))(3)) were realized from the reaction of M(OBu(t))(4) (M = Ti, Zr, Hf) and H-ONep. Crystallization of 1 from py led to the isolation of [Ti(µ-ONep)(ONep)(3)](2)(µ-py) (1a) whereas the dissolution of 2 or 3 in py yielded {(µ(3)-O)(µ(3)-OBu(t))[(µ-ONep)M(ONep)(2)](3)} M = Zr (2a) and Hf (3a). The structurally similar congener set of 1-3 was used to investigate variations of their resultant nanomaterials under solvothermal conditions at high (10 M KOH), low (conc. (aq) HI), and neutral (H(2)O) pH conditions. Reproducible nanodots, -squares, and -rods of varied aspect ratios were isolated based on cation and the reaction pH. The hydrolysis products were reasoned to be the "seed" nucleation sites in these processes, and studying the hydrolysis behavior of 1-3 led to the identification of [Ti(6)(µ(3)-O)(7)(µ-O)(µ-ONep)(2)(ONep)(6)](2) (1b) for 1 but yielded 2a and 3a for 2 and 3, respectively. A correlation was found to exist between these products and the final nanomaterials formed for the acidic and neutral processes. The basic route appears to be further influenced by another property, possibly associated with the solubility of the final nanoceramic material.

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

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(2)CCH(CH(3))(2), H-OBc (H-O(2)CC(CH(3))(3), H-ONc (H-O(2)CCH(2)C(CH(3))(3))] were individually reacted with diethyl zinc (ZnEt(2)) to yield a set of previously unidentified zinc carboxylates: (i) [Zn(mu-ORc)(3)Zn(mu-ORc)](n) [ORc = OPc (1), ONc (2)], (ii) [(py)Zn](2)(mu-ORc)(4) [ORc = OBc (3), ONc (4), and py = pyridine], or (iii) Zn(ORc)(2)(solv)(2) [ORc/solv = OPc/py (5), O(c)Nc/H(2)O (6) (O(c)Rc = 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(c)Bc)Ln[(mu-OBc)(3)Zn(py)](2) [Ln = Pr (7), Nd (8), Sm (9)] or (ii) (py)(2)Zn(mu-OBc)(3)Ln(O(c)Bc)(2)(py) [Ln = Tb (10), Dy (11), Er (12), Y (13), Yb (14)]. Exploration of alternative starting materials [Ln(NO(3))(3).nH(2)O, Zn(O(2)CCH(3))(2), HOBc in py] led to the isolation of (NO(3)(c))Ln[(mu-OBc)(3)Zn(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.

Structural Characterization of Methanol Substituted Lanthanum Halides.

The first study into the alcohol solvation of lanthanum halide [LaX(3)] derivatives as a means to lower the processing temperature for the production of the LaBr(3) scintillators was undertaken using methanol (MeOH). Initially the de-hydration of {[La(micro-Br)(H(2)O)(7)](Br)(2)}(2) (1) was investigated through the simple room temperature dissolution of 1 in MeOH. The mixed solvate monomeric [La(H(2)O)(7)(MeOH)(2)](Br)(3) (2) compound was isolated where the La metal center retains its original 9-coordination through the binding of two additional MeOH solvents but necessitates the transfer of the innersphere Br to the outersphere. In an attempt to in situ dry the reaction mixture of 1 in MeOH over CaH(2), crystals of [Ca(MeOH)(6)](Br)(2) (3) were isolated. Compound 1 dissolved in MeOH at reflux temperatures led to the isolation of an unusual arrangement identified as the salt derivative {[LaBr(2.75)*5.25(MeOH)](+0.25) [LaBr(3.25)*4.75(MeOH)](-0.25)} (4). The fully substituted species was ultimately isolated through the dissolution of dried LaBr(3) in MeOH forming the 8-coordinated [LaBr(3)(MeOH)(5)] (5) complex. It was determined that the concentration of the crystallization solution directed the structure isolated (4 concentrated; 5 dilute) The other LaX(3) derivatives were isolated as [(MeOH)(4)(Cl)(2)La(micro-Cl)](2) (6) and [La(MeOH)(9)](I)(3)*MeOH (7). Beryllium Dome XRD analysis indicated that the bulk material for 5 appear to have multiple solvated species, 6 is consistent with the single crystal, and 7 was too broad to elucidate structural aspects. Multinuclear NMR ((139)La) indicated that these compounds do not retain their structure in MeOD. TGA/DTA data revealed that the de-solvation temperatures of the MeOH derivatives 4 - 6 were slightly higher in comparison to their hydrated counterparts.

Homo- and heterometallic complexes of tetra-(di-substituted hydroxybenzyl)-N,N'-ethylenediamine derivatives.

The coordination behavior of a series of group 4 metal alkoxides [M(OR)(4)] modified by a set of novel substituted hydroxybenzyl ethylene diamine (H(4)-ED-L(4)) ligands {[tetra(3,5-di-t-butyl-2-hydroxybenzyl)-N,N'-ethylenediamine] termed H(4)-ED-DBP(4) (1), [tetra(3,5-di-t-amyl-2-hydroxybenzyl)-N,N'-ethylenediamine] termed H(4)-ED-DAP(4) (1a), and [tetra(3,5-dichloro-2-hydroxybenzyl)-N,N'-ethylenediamine] termed H(4)-ED-DCP(4) (2)} was elucidated. The reaction of 1 or 1a with the M(OR)(4) precursor led to the isolation of the structural similar species M(ED-L(4)) where L = DBP, M = Ti (3), Zr (4), Hf (5); L = DAP, M = Zr (4a), Hf (5a). In contrast, the reaction of 2 with the M(OR)(4) precursors yielded Ti(ED-DCP(4)) (6), (py)(2)Zr(ED-DCP(4)) (7), and (HOBu(t))Hf(ED-DCP(4)) (8) where py = pyridine and HOBu(t) = HOC(CH(3))(3). For 3-6, the cations of the monomeric species were completely encapsulated by all available heteroatoms (four O and two N) of the ED-L(4) ligands, yielding an octahedral geometry for each metal center. For 7 and 8, an identical binding by the ED-DCP(4) ligand was observed with the additional coordination of Lewis basic adducts, forming 8- and 7-coordinated metal centers, respectively. Switching to +2 cations led to the isolation of [(THF)Ca](2)(ED-DBP(4)) (9a) where THF = tetrahydrofuran, {[(py)Ca](4)(ED-(mu-DBP-eta(6))(4))(2)}(n) (9b), and [(py)Zn](ED-DBP(4))[Zn(py)(2)] (10) *5py and [(py)Sn](2)(ED-DBP(4)) (11). The structures of these species were significantly different in arrangement compared to the Group 4 derivatives. Further attempts to produce a mixed +4/+2 cationic species yielded [(py)(ONep)(2)Ti(ED-DBP(4))Zn(py)] (12). Reacting the single-source precursor Co[mu-OC(6)H(4)(CHMe(2))(2)-2)(2)Li(py)(2)](2) with 1, led to the isolation of (py)Li[ED-DBP(3)(H-DBP)]Co (13), with one of the phenol protons remaining unreacted. The synthesis and characterization of these compounds are presented in detail.

Synthesis and Characterization of Germanium Coordination Compounds for Production of Germanium Nanomaterials.

A series of novel germanium(II) precursors was synthesized to initiate an investigation between the precursors' structures and the morphologies of the resulting nanoparticles. The precursors were synthesized from the reaction of Ge[N(SiMe3)2]2 or [Ge(OBut)2]2 and the appropriate ligand: N,N'-dibenzylethylenediamine (H2-DBED), tert-butanol (H-OBut), 2,6-di-methyl phenol (H-DMP), 2,6-di-phenyl phenol (H-DPP), tert-butyldimethylsilanol (H-DMBS), triphenylsilanol (H-TPS), triphenylsilanethiol (H-TPST), and benzenethiol (H-PS). The products were identified as: [Ge(µc-DBED)]2 (1, µc= bridging chelating), [Ge(µ-DMP)(DMP)]2 (2), Ge(DPP)2 (3), [Ge(µ-OBut)(DMBS)]2, (4), [Ge(µ-DMBS)(DMBS)]2 (5), Ge(TPS)3(H) (6), [Ge(µ-TPST)(TPST)]2 (7), and Ge(PS)4 (8). The Ge(II) metal centers were found to adopt a pyramidal geometry for 1, 2, 4, 5, 7, a bent arrangement for 3, and a tetrahedral coordination for the Ge(IV) species 6 and 8. Using a simple solution precipitation methodology, Ge(0) nanomaterials were isolated as dots and wires for the majority of precursors. Compound 7 led to the isolation of amorphous GexSy. The nanomaterials isolated were characterized by TEM, EDS, and powder XRD. A correlation between the precursor's arrangement and final observed nanomorphology was proffered as part of the 'precursor structure affect' phenomenon.

Stepwise modification of titanium alkoxy chloride compounds by pyridine carbinol.

The stepwise modifications of stoichiometric mixtures of titanium chloride (TiCl 4) and titanium iso-propoxide (Ti(OPr (i)) 4) by 2-pyridine methanol (H-OPy) led to the isolation of a systematically varied, novel family of compounds. The 3:1 reaction mixture of Ti(OPr (i)) 4:TiCl 4 yielded [Cl(OPr (i)) 2Ti(mu-OPr (i))] 2 ( 1). Modification of 1 with 1 and 2 equiv of H-OPy produced [Cl(OPr (i)) 2Ti(mu c-OPy)] 2 ( 2, where mu c = chelating bridge) and "(OPy) 2TiCl(OPr (i))" ( 3, not crystallographically characterized), respectively. Altering the Ti(OPr (i)) 4 to TiCl 4 stoichiometry to 1:1 led to isolation and identification of another dimeric species [Cl 2(OPr (i))Ti(mu-OPr (i))] 2 ( 4). Upon modification with 1 equiv of H-OPy, [Cl 2(OPr (i))Ti(mu c-OPy)] 2 ( 5) was isolated from toluene and (OPy)TiCl 2(OPr (i))(py) ( 6) from py. An additional equivalent of H-OPy led to the monomeric species (OPy) 2TiCl 2 ( 7). Because of the low solubility and similarity in constructs of these compounds, additional analytical data, such as the beryllium dome or BeD-XRD powder analyses, were used to verify the bulk samples, which were found to be in agreement with the single crystal structures.

2-(Hydroxy-meth-yl)pyridinium chloride.

In the title molecular salt, C(6)H(8)NO(+)·Cl(-), the packing is consolidated by N-H⋯Cl and O-H⋯Cl hydrogen bonds, resulting in the formation of [010] chains of alternating cations and anions.

Isostructural neo-pentoxide derivatives of group 3 and the lanthanide series metals for the production of Ln2O3 nanoparticles.

The synthesis and characterization of a series of neo-pentoxide (OCH2C(CH3)3 or ONep) derivatives of group 3 and the lanthanide (Ln) series' metals were undertaken via an amide/alcohol exchange route. Surprisingly, the products isolated and characterized by single-crystal X-ray diffraction yielded isostructural species for every trivalent cation studied: [Ln(mu-ONep)2(ONep)]4 [Ln=Sc (1), Y (2), La (3), Ce (4), Pr (5), Nd (6), Sm (7), Eu (8), Gd (9), Tb (10), Dy (11), Ho (12), Er (13), Tm (14), Yb (15), Lu (16)]. Compounds 3, 4, 6, and 11 have been previously reported. Within this series of complexes, the Ln metal centers are oriented in a square with each Ln-Ln edge interconnected via two mu-ONep ligands; each metal center also binds one terminal ONep ligand. NMR data of 1-3 indicate that the solid-state structure is retained in solution. FTIR spectroscopy (KBr pellet) revealed the presence of significant Ln---H-C interactions within one set of the bridging ONep ligands in all cases; the stretching frequencies of these C-H bonds appear to increase in magnitude with decrease in metal ion radius. These complexes were used to generate nanoparticles through solution hydrolysis routes, resulting in the formation of lanthanide oxide nanoparticles and rods. The emission properties of these ceramics were preliminarily investigated using UV-vis and PL measurements.

Controlled synthesis of a structurally characterized family of sterically constrained heterocyclic alkoxy-modified titanium alkoxides.

The reaction of [Ti(mu-ONep)(ONep)3]2 (ONep = OCH2C(CH3)3) with a series of heterocyclic methanol derivatives [tetrahydrofurfuryl alcohol (H-OTHF), thiophene methanol (H-OTPM), or 2-pyridylcarbinol (H-OPy)-collectively termed H-OR*], led to the isolation of a novel family of OR*-substituted titanium alkoxide precursors. Independent of the initial stoichiometry for the H-OTHF reaction, a monosubstituted, dinuclear species was isolated as [(ONep)3Ti(muc-OTHF)]2 (1). For 1, each Ti was octahedrally (Oh) bound by three terminal ONep ligands, one bidentate bridging OTHF ligand (muc-OTHF), and an oxygen from the other muc-OTHF ligand. For the OTPM derivatives, the product was identified as [(ONep)3Ti(mu-OTPM)]2 (2). For this ligand, the soft S atom does not bind to the Ti but the O atom does act as a bridge between the two trigonal bipyramidal bound Ti metal centers. The OPy system yielded (OPy)2Ti(OR)2 independent of the OR and the stoichiometry used [OR = ONep (3), OCHMe2 (4), OCMe3 (5)]. For 3-5, the two OPy ligands chelate to the Oh-bound Ti metal center with two terminal OR ligands. Compounds 1-5 were fully characterized using a variety of analytical techniques. An initial investigation of the proposed chemical stability of the '(OPy)2Ti' moiety of 3-5 to alcoholysis exchange pathways involving (i) alkyl alcohols, (ii) aryl alcohols, (iii) substituted phenols, (iv) H-OR* derivatives, and (v) silanols proved successful through the isolation of a novel family of structurally characterized (OPy)2Ti(OR')2 (7-24) compounds.

Synthesis and characterization of a family of structurally characterized dysprosium alkoxides for improved fatigue-resistance characteristics of PDyZT thin films.

Using either an ammoniacal route, the reaction between DyCl3, Na0, and HOR in liquid ammonia, or preferentially reacting Dy(N(SiMe3)2)3 with HOR in a solvent, we isolated a family of dysprosium alkoxides as [Dy(mu-ONep)2(ONep)]4 (1), (ONep)2Dy[(mu3-ONep)(mu-ONep)Dy(ONep)(THF)]2(mu-ONep) (2), (ONep)2Dy[(mu3-ONep)(mu-ONep)Dy(ONep)(py)]2(mu-ONep) (3), [Dy3(mu3-OBut)2(mu-OBut3(OBut)4(HOBut)2] (4), [Dy3(mu3-OBut)2(mu-OBut)3(OBut)4(THF)2] (5), [Dy3(mu3-OBut)2(mu-OBut)3(OBut)4(py)2] (6), (DMP)Dy(mu-DMP)4[Dy(DMP)2(NH3)]2 (7), [Dy(eta6-DMP)(DMP)2]2 (8), Dy(DMP)3(THF)3 (9), Dy(DMP)3(py)3 (10), Dy(DIP)3(NH3)2 (11), [Dy(eta6-DIP)(DIP)2]2 (12), Dy(DIP)3(THF)2 (13), Dy(DIP)3(py)3 (14), Dy(DBP)3(NH3) (15), Dy(DBP)3 (16), Dy(DBP)3(THF) (17), Dy(DBP)3(py)2 (18), [Dy(mu-TPS)(TPS2]2 (19), Dy(TPS)3(THF)3 (20), and Dy(TPS)3(py)3 (21), where ONep = OCH2CMe3, OBut) = OCMe3, DMP = OC6H3(Me)(2)-2,6, DIP = OC6H3(CHMe2)(2)-2,6, DBP = OC6H3(CMe3)(2)-2,6, TPS = OSi(C6H5)3, tol = toluene, THF = tetrahydrofuran, and py = pyridine. We were not able to obtain X-ray quality crystals of compounds 2, 8, and 9. The structures observed and data collected for the Dy compounds are consistent with those reported for its other congeners. A number of these precursors were used as Dy dopants in Pb(Zr0.3Ti0.7)O3 (PZT 30/70) thin films, with compound 12 yielding the highest-quality films. The resulting Pb0.94Dy0.04(Zr0.3Ti0.7)O3 [PDyZT (4/30/70)] had similar properties to PZT (30/70), but showed substantial resistance to polarization reversal fatigue.