Electronic and Molecular Structures of a Series of Nickel Bis-1,1-Dithiolates.

A series of homoleptic Ni bis-1,1-dithiolates, [Ni(S2C2RR')2]2- (R = CN, R' = CN, CO2Et, CONH2, Ph, Ph-4-Cl, Ph-4-OMe, Ph-4-NO2, Ph-3-CF3, Ph-4-CF3, Ph-4-CN; R = NO2, R' = H; R = R' = CO2Et) have been synthesized from the reaction of the alkali metal salt of the ligand and nickel chloride, and isolated as tetraphenylphosphonium or tetrabutylammonium salts. The complexes were characterized by X-ray crystallography, high-resolution mass spectrometry, and infrared (IR), nuclear magnetic resonance (NMR) and electronic absorption spectroscopies. The molecular structures show a rigidly square planar Ni(II) center linking two four-membered chelate rings whose dimensions are constant across the series. The electronic effect of the ligand substituents are revealed in the 13C NMR and electronic spectra, and corroborated by density functional calculations. Electron withdrawing groups deshield the low-field CS2 resonance, and the signature charge transfer band in the visible region is red-shifted. These observables have been accurately reproduced computationally, and revealed the Ni contribution to the ground state diminishes with decreasing electron withdrawing capacity of the ligand substituents. In contrast to 1,2-dithiolates, the redox inactivity afforded by 1,1-dithiolates stems from the smaller chelate ring and substantially reduced sulfur content that is key to stabilizing the radical form.

A Mechanistic Investigation of the N-Hydroxyphthalimide Catalyzed Benzylic Oxidation Mediated by Sodium Chlorite.

A detailed investigation into the mechanistic course of N-hydroxyphthalimide catalyzed oxidation of benzylic centers using sodium chlorite as the stoichiometric oxidant is reported. Through a combination of experimental, spectroscopic, and computational techniques, the transformation is interrogated, providing improved reaction conditions and an enhanced understanding of the mechanism. Performing the transformation in the presence of acetic acid or a pH 4.5 buffer leads to extended reaction times but improves the catalyst lifetime, leading to the complete consumption of the starting material. Chlorine dioxide is identified as the active oxidant that is able to oxidize the N-hydroxyphthalimide anion to the phthalimide-N-oxyl radical, the proposed catalytically active species, which is able to abstract a hydrogen atom from the substrate. A second molecule of chlorine dioxide reacts with the resultant radical and, after loss of hypochlorous acid, leads to the observed product. Through a broad variety of techniques including UV/vis, EPR and Raman spectroscopy, isotopic labeling, and the use of radical traps, evidence for the mechanism is presented that is supported through electronic structural calculations.

Asymmetric by Design: Heteroleptic Coordination Compounds with Redox-Active Dithiolene and 1,2,4,5-Tetrakis(isopropylthio)benzene Ligands.

The 1,2,4,5-tetrakis(alkylthio)benzenes are redox-active organosulfur molecules that support oxidation to a stable radical cation. Their utility as ligands for the assembly of multimetal complexes with tailored functionality/property is unexamined. Here, 1,2,4,5-tetrakis(isopropylthio)benzene (tptbz, 1) is shown to bind PdCl2 at either one end, leaving the other open, or at both ends to form centrosymmetric [Cl2Pd(tptbz)PdCl2], 4. Ligand metathesis between Na2[(N≡C)2C2S2] (Na2mnt) and [Cl2M(tptbz)] (M = Pd, 2; M = Pt, 3) yields [(mnt)M(tptbz)] (M = Pd, 5; M = Pt, 6), but an alternative route involving transmetalation with [(mnt)SnMe2] delivers substantially greater yield. The mixed dithiolene-dithioether compound [(Ph2C2S2)Pt(tptbz)] (8) is formed by a similar transmetalation protocol using [(Ph2C2S2)SnnBu2]. Compounds 5, 6, and 8 are the first such heteroleptic complexes prepared by deliberate synthesis. The cyclic voltammetry of 8 reveals anodic waves at +0.14 and +0.97 V vs Fc+/Fc, which are attributed to successive dithiolene oxidation processes. While oxidized at +0.73 V as a free ligand, the redox-active MO of tptbz is pushed to a higher potential upon coordination to Pt2+ and is inaccessible. Calculations of the structures of [8]+ and of [((Cl2-3,5-C6H3)2C2S2)Pt(tptbz)]+ show that, in the latter, the dithiolene MOs are drawn down in energy into proximity with the tptbz MOs.

Fully Reduced and Mixed-Valent Multi-Copper Aggregates Supported by Tetradentate Diamino Bis(thiolate) Ligands.

Tetradentate diamino bis(thiolate) ligands (l-N2S2(2-)) with saturated linkages between heteroatoms support fully reduced [(Cu(l-N2S2))2Cu2] complexes that bear relevance as an entry point toward molecules featuring the Cu2ICu2II(µ4-S) core composition of nitrous oxide reductase (N2OR). Tetracopper [(Cu(l-N2(SMe2)2))2Cu2] (l-N2(SMe2H)2 = N1,N2-bis(2-methyl-2-mercaptopropane)-N1,N2-dimethylethane-1,2-diamine) does not support clean S atom oxidative addition but undergoes Cl atom transfer from PhICl2 or Ph3CCl to afford [(Cu(l-N2(SMe2)2))3(CuCl)5], 14. When introduced to Cu(I) sources, the l-N2(SArH)2 ligand (l-N2(SArH)2 = N1,N2-bis(2-mercaptophenyl)-N1,N2-dimethylethane-1,2-diamine), made by a newly devised route from N1,N2-bis(2-fluorophenyl)-N1,N2-dimethylethane-1,2-diamine, ultimately yields the mixed-valent pentacopper [(Cu(l-N2SAr2))3Cu2] (19), which has 3-fold rotational symmetry (D3) around a Cu2 axis. The single CuII ion of 19 is ensconced within an equatorial l-N2(SAr)2(2-) ligand, as shown by 14N coupling in its EPR spectrum. Formation of 19 proceeds from an initial, fully reduced product, [(Cu(l-N2SAr2))3Cu2(Cu(MeCN))] (17), which is C2 symmetric and exceedingly air-sensitive. While unreactive toward chalcogen donors, 19 supports reversible reduction to the all-cuprous state; generation of [19]1- and treatment with S atom donors only return 19 because structural adjustments necessary for oxidative addition are noncompetitive with outer-sphere electron transfer. Oxidation of 19 is marked by intense darkening, consistent with greater mixed valency, and by dimerization in the crystalline state to a decacopper species ([20]2+) of S4 symmetry.

A Self-Assembling Flavin for Visible Photooxidation.

A new flavin-based gelator is reported which forms micellar structures at high pH and gels at low pH. This flavin can be used for the photooxidation of thiols under visible light, with the catalytic efficiency being linked to the self-assembled structures present.

Role of the Meso Substituent in Defining the Reduction of Uranyl Dipyrrin Complexes.

The uranyl complex UVIO2Cl(LMes) of the redox-active, acyclic dipyrrin-diimine anion LMes- [HLMes = 1,9-di-tert-butyl-imine-5-(mesityl)dipyrrin] is reported, and its redox property is explored and compared with that of the previously reported UVIO2Cl(LF) [HLF = 1,9-di-tert-butyl-imine-5-(pentafluorophenyl)dipyrrin] to understand the influence of the meso substituent. Cyclic voltammetry, electron paramagnetic resonance spectroscopy, and density functional theory studies show that the alteration from an electron-withdrawing meso substituent to an electron-donating meso substituent on the dipyrrin ligand significantly modifies the stability of the products formed after reduction. For UVIO2Cl(LMes), the formation of a diamond-shaped, oxo-bridged uranyl(V) dimer, [UVO2(LMes)]2 is seen, whereas in contrast, for UVIO2Cl(LF), only ligand reduction occurs. Computational modeling of these reactions shows that while ligand reduction followed by chloride dissociation occurs in both cases, ligand-to-metal electron transfer is favorable for UVIO2Cl(LMes) only, which subsequently facilitates uranyl(V) dimerization.

Exploring the Redox Properties of Bench-Stable Uranyl(VI) Diamido-Dipyrrin Complexes.

The uranyl complexes UO2(OAc)(L) and UO2Cl(L) of the redox-active, acyclic diamido-dipyrrin anion L- are reported and their redox properties explored. Because of the inert nature of the complexes toward hydrolysis and oxidation, synthesis of both the ligands and complexes was conducted under ambient conditions. Voltammetric, electron paramagnetic resonance spectroscopy, and density functional theory studies show that one-electron chemical reduction by the reagent CoCp2 leads to the formation of a dipyrrin radical for both complexes [Cp2Co][UO2(OAc)(L•)] and [Cp2Co][UO2Cl(L•)].

Heterotrimetallic Assemblies with 1,2,4,5-Tetrakis(diphenylphosphino)benzene Bridges: Constructs for Controlling the Separation and Spatial Orientation of Redox-Active Metallodithiolene Groups.

Metallodithiolene complexes of the type [(R2C2S2)M(η2-tpbz)] [R = CN, Ph, or p-anisyl; M = Ni2+, Pd2+, or Pt2+; tpbz = 1,2,4,5-tetrakis(diphenylphosphino)benzene] chelate transition metals ions to form trimetallic arrays [[(R2C2S2)M(tpbz)]2M']n+, where M' is square planar Pt2+, tetrahedral Cu+, Ag+, or Au+, or octahedral {ReBr(CO)}/{Re(CO)2}+. Forcing conditions (190 °C reflux in decalin, 72 h) are demanded for the Re+ compounds. With third-row metals at the nexus, the compounds are stable to air. Twelve members of the set have been characterized by X-ray diffraction and reveal dithiolene centroid-centroid distances ranging from 22.4 to 24.0 Å. Folding around each tpbz intrachelate P···P axis such that the MP2/M'P2 planes meet the tpbz P2C6P2 mean plane at non-zero values gives rise to core topologies that appear "S-like" or herringbone-like for M' = Pt2+ or {ReBr(CO)}/{Re(CO)2}+. Calculations reveal that departure from idealized D2h/D2d/C2v symmetries is induced by steric crowding between Ph groups and that dynamic, fluxional behavior is pertinent to the solution phase because multiple, lower-symmetry minima of comparable energy exist. Spectroscopically, the formation of the trimetallic arrays is marked by a shift of the open end 31P nuclear magnetic resonance signal from approximately -14.5 ppm to approximately +41, approximately +20.5, and approximately +28.5 ppm for M' = Pt2+, Au+, and {ReBr(CO)}/{Re(CO)2}+, respectively. Electrochemically, dithiolene-based oxidations are observed for the R = Ph and M' = Pt2+ or Au+ compounds but at potentials that are anodically shifted relative to charge-neutral [[(R2C2S2)M]2(µ-tpbz)]. The compounds reported clarify the possibilities for the synthesis of assemblies in which weakly coupled spins may be created in their modular (R2C2S2)M and M' parts.

Oxo versus Sulfido Coordination at Tungsten: A Spectroscopic and Correlated Ab Initio Electronic Structure Study.

The tungsten ion that resides at the active site of a unique class of enzymes only found in esoteric hyperthermophilic archaea bacteria is known to possess at least one terminal chalcogenide ligand. The identity of this as either an oxo or sulfido (or both) is difficult to ascertain from structural studies; therefore, small-molecule analogues are developed to calibrate and substantiate spectroscopic signatures obtained from native proteins. The electronic structures of Tp*WECl2 (E = O, S; Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate) have been scrutinized using electronic, electron paramagnetic resonance (EPR), and X-ray absorption spectroscopy to assess the impact of terminal chalcogen on the adjacent cis chloride ligands. Examination at the Cl K-edge provides a direct probe of the bonding and therein lability of these chloride ligands, and in conjunction with density functional theoretical and multireference calculations reveals greater bond covalency in Tp*WOCl2 compared to Tp*WSCl2. The computational model and electronic structure assignment are corroborated by the reproduction of spin-Hamiltonian parameters, whose magnitude is dominated by the sizeable spin-orbit coupling of tungsten.

Open-Ended Metallodithiolene Complexes with the 1,2,4,5-Tetrakis(diphenylphosphino)benzene Ligand: Modular Building Elements for the Synthesis of Multimetal Complexes.

Open-ended, singly metalated dithiolene complexes with 1,2,4,5-tetrakis(diphenylphosphino)benzene (tpbz) are prepared either by ligand transfer to [Cl2M(tpbz)] from (R2C2S2)SnR'2 (R = CN, R' = Me; R = Me, R' = nBu) or by a direct reaction between tpbz and [M(S2C2R2)2] (M = Ni, Pd, Pt; R = Ph, p-anisyl) in a 1:1 ratio. The formation of dimetallic [(R2C2S2)M(tpbz)M(S2C2R2)] attends these syntheses in modest amounts, but the open-ended compounds are readily separated by silica chromatography. As affirmed by X-ray crystallographic characterization of numerous members of the set, the [(R2C2S2)M(tpbz)] compounds show dithiolene ligands in their fully reduced ene-1,2-dithiolate form conjoined with divalent Group 10 ions. Minor amounts of octahedral [(Ph2C2S2)2PtIV(tpbz)], a presumed intermediate, are isolated from the preparation of [(Ph2C2S2)PtII(tpbz)]. Heterodimetallic [(Ph2C2S2)Pt(tpbz)Ni(S2C2Me2)] is prepared from [(Ph2C2S2)PtII(tpbz)]; its cyclic voltammogram, upon anodic scanning, shows two pairs of closely spaced, but resolved, 1e- oxidations corresponding first to [R2C2S22-] - 1e- → [R2C2S•S-] and then to [R2C2S•S-] - 1e- → [R2(C═S)2]. The open diphosphine of [(R2C2S2)M(tpbz)] can be oxidized to afford open-ended [(R2C2S2)M(tpbzE2)] (E = O, S). Synthesis of the octahedral [(dppbO2)3Ni][I3]2 [dppbO2 = 1,2-bis(diphenylphosphoryl)benzene] suggests that the steric profile of [(R2C2S2)M(tpbzE2)] is moderated enough that three could be accommodated as ligands around a metal ion.

Investigating Complex Magnetic Anisotropy in a Co(II) Molecular Compound: A Charge Density and Correlated Ab Initio Electronic Structure Study.

Understanding magnetic anisotropy and specifically how to tailor it is crucial in the search for high-temperature single-ion magnets. Herein, we investigate the magnetic anisotropy in a six-coordinated cobalt(II) compound that has a complex geometry and distinct triaxial magnetic anisotropy from the perspective of the electronic structure, using electronic spectra, ab initio calculations, and an experimental charge density, of which the latter two provides insight into the d-orbital splitting. The analysis showed that the d-orbital splitting satisfactorily predicted the complex triaxial magnetic anisotropy exhibited by the compound. Furthermore, a novel method to directly compare the ab initio results and the d-orbital populations obtained from the experimental charge density was developed, while a topological analysis of the density provided insights into the metal-ligand bonding. This work thus further establishes the validity of using d-orbitals for predicting magnetic anisotropy in transition metal compounds while also pointing out the need for a more frequent usage of the term triaxial anisotropy in the field of single-molecule magnetism.

Heteroleptic Samarium(III) Chalcogenide Complexes: Opportunities for Giant Exchange Coupling in Bridging σ- and π-Radical Lanthanide Dichalcogenides.

The introduction of (N2)3-• radicals into multinuclear lanthanide molecular magnets raised hysteresis temperatures by stimulating strong exchange coupling between spin centers. Radical ligands with larger donor atoms could promote more efficient magnetic coupling between lanthanides to provide superior magnetic properties. Here, we show that heavy chalcogens (S, Se, Te) are primed to fulfill these criteria. The moderately reducing Sm(II) complex, [Sm(N††)2], where N†† is the bulky bis(triisopropylsilyl)amide ligand, can be oxidized (i) by diphenyldichalcogenides E2Ph2 (E = S, Se, Te) to form the mononuclear series [Sm(N††)2(EPh)] (E = S, 1-S; Se, 1-Se, Te, 1-Te); (ii) S8 or Se8 to give dinuclear [{Sm(N††)2}2(µ-η2:η2-E2)] (E = S, 2-S2; Se, 2-Se2); or (iii) with Te═PEt3 to yield [{Sm(N††)2}(µ-Te)] (3). These complexes have been characterized by single crystal X-ray diffraction, multinuclear NMR, FTIR, and electronic spectroscopy; the steric bulk of N†† dictates the formation of mononuclear complexes with chalcogenate ligands and dinuclear species with the chalcogenides. The Lα1 fluorescence-detected X-ray absorption spectra at the Sm L3-edge yielded resolved pre-edge and white-line peaks for 1-S and 2-E2, which served to calibrate our computational protocol in the successful reproduction of the spectral features. This method was employed to elucidate the ground state electronic structures for proposed oxidized and reduced variants of 2-E2. Reactivity is ligand-based, forming species with bridging superchalcogenide (E2)-• and subchalcogenide (E2)3-• radical ligands. The extraordinarily large exchange couplings provided by these dichalcogenide radicals reveal their suitability as potential successors to the benchmark (N2)3-• complexes in molecular magnets.

Modulating the Magnetic Properties of Copper(II)/Nitroxyl Heterospin Complexes by Suppression of the Jahn-Teller Distortion.

A series of six-coordinate [Cu(L)L1][BF4]2 (L1 = 2,6-bis{1-oxyl-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-2-yl}pyridine) complexes are reported. Ferromagnetic coupling between the Cu and L1 ligand spins is enhanced by an L coligand with distal methyl substituents, which is attributed to a sterically induced suppression of its Jahn-Teller distortion.

Durable infrared optical coatings based on pulsed DC-sputtering of hydrogenated amorphous carbon (a-C:H).

Optical properties of low-temperature pulsed DC-sputter deposited ($ {\le} {70° {\rm C}}$≤70°C) hydrogenated carbon are presented. Increasing hydrogen incorporation into the sputter deposited carbon significantly decreases infrared optical absorption due to a decrease in deep absorptive states associated with dangling bonds. Hydrogen flow is optimized (hydrogen flow 3 sccm), achieving the best compromise between increased infrared transmittance and hardness for durable coating performance. Optical, environmental, and durability performance of pulsed DC-sputtered carbon incorporated in multilayer (a-C:H/Ge) infrared antireflective coatings indicates suitability as a durable infrared optical coating for commonly used infrared substrates, including temperature sensitive chalcogenide glass.

Kinetic Control of Interpenetration in Fe-Biphenyl-4,4'-dicarboxylate Metal-Organic Frameworks by Coordination and Oxidation Modulation.

Phase control in the self-assembly of metal-organic frameworks (MOFs) is often a case of trial and error; judicious control over a number of synthetic variables is required to select the desired topology and control features such as interpenetration and defectivity. Herein, we present a comprehensive investigation of self-assembly in the Fe-biphenyl-4,4'-dicarboxylate system, demonstrating that coordination modulation can reliably tune between the kinetic product, noninterpenetrated MIL-88D(Fe), and the thermodynamic product, two-fold interpenetrated MIL-126(Fe). Density functional theory simulations reveal that correlated disorder of the terminal anions on the metal clusters results in hydrogen bonding between adjacent nets in the interpenetrated phase and this is the thermodynamic driving force for its formation. Coordination modulation slows self-assembly and therefore selects the thermodynamic product MIL-126(Fe), while offering fine control over defectivity, inducing mesoporosity, but electron microscopy shows MIL-88D(Fe) persists in many samples despite not being evident by diffraction. Interpenetration control is also demonstrated using the 2,2'-bipyridine-5,5'-dicarboxylate linker; it is energetically prohibitive for it to adopt the twisted conformation required to form the interpenetrated phase, although multiple alternative phases are identified due to additional coordination of Fe cations to its N donors. Finally, we introduce oxidation modulation-the use of metal precursors in different oxidation states from that found in the final MOF-to kinetically control self-assembly. Combining coordination and oxidation modulation allows the synthesis of pristine MIL-126(Fe) with BET surface areas close to the predicted maximum for the first time, suggesting that combining the two may be a powerful methodology for the controlled self-assembly of high-valent MOFs.

Enhanced Fe-Centered Redox Flexibility in Fe-Ti Heterobimetallic Complexes.

Previously, we reported the synthesis of Ti[N( o-(NCH2P( iPr)2)C6H4)3] and the Fe-Ti complex, FeTi[N( o-(NCH2P( iPr)2)C6H4)3], abbreviated as TiL (1), and FeTiL (2), respectively. Herein, we describe the synthesis and characterization of the complete redox families of the monometallic Ti and Fe-Ti compounds. Cyclic voltammetry studies on FeTiL reveal both reduction and oxidation processes at -2.16 and -1.36 V (versus Fc/Fc+), respectively. Two isostructural redox members, [FeTiL]+ and [FeTiL]- (2ox and 2red, respectively) were synthesized and characterized, along with BrFeTiL (2-Br) and the monometallic [TiL]+ complex (1ox). The solid-state structures of the [FeTiL]+/0/- series feature short metal-metal bonds, ranging from 1.94-2.38 Å, which are all shorter than the sum of the Ti and Fe single-bond metallic radii (cf. 2.49 Å). To elucidate the bonding and electronic structures, the complexes were characterized with a host of spectroscopic methods, including NMR, EPR, and 57Fe Mössbauer, as well as Ti and Fe K-edge X-ray absorption spectroscopy (XAS). These studies, along with hybrid density functional theory (DFT) and time-dependent DFT calculations, suggest that the redox processes in the isostructural [FeTiL]+,0,- series are primarily Fe-based and that the polarized Fe-Ti π-bonds play a role in delocalizing some of the additional electron density from Fe to Ti (net 13%).

Comment on "Stabilization of Low-Valent Iron(I) in a High-Valent Vanadium(V) Oxide Cluster".

A recent Communication in this journal reported the stabilization of low-valent iron(I) in a fully oxidized polyoxovanadate. With no ligand-field argument to support such an assignment, a re-evaluation of the data accompanied by detailed computational analysis reveals the redox chemistry is localized to the polyoxovanadate, and when reduced, instigates a spin transition at iron.

Controlled Tuning of the Properties in Optoelectronic Self-Sorted Gels.

Multicomponent supramolecular gels have great potential for optoelectronics. Ideally, we could control the self-assembly of multiple components across many length scales, from the primary assembled structures to how these are arranged in space. This would allow energy transfer between p-type and n-type fibers to be controlled. Usually, a single network is formed and analyzed. It is not clear how most networks could be modified, and certainly not how these might be differentiated. Here, we address both of these issues. We show how the different components in a multicomponent gel can be differentiated by small-angle neutron scattering using contrast-matching experiments. The rate of self-assembly can be used to vary the networks that are formed, leading directly to changes in the efficiency of electron transfer. The assembly kinetics can therefore be used to prepare different networks from the same primary building blocks and primary self-assembled structures. We expect that these advances will allow multicomponent systems to become effective electronic materials.

Ligand Radicals as Modular Organic Electron Spin Qubits.

The intrinsic redox activity of the dithiolene ligand is presented here as the novel spin host in the design of a prototype molecular electron spin qubit, where the traditional roles of the metal and ligand components in coordination complexes are inverted. A series of paramagnetic bis(dithiolene) complexes with group 10 metals-nickel, palladium, platinum-provides a backdrop to investigate the spin dynamics of the organic ligand radical using pulsed EPR spectroscopy. The temperature dependence of the phase memory time (TM ) is shown to be dependent on the identity of the diamagnetic metal ion, with the short times recorded for platinum a consequence of a diminishing spin-lattice (T1 ) relaxation time driven by spin-orbit coupling. The utility of the radical ligand spin center is confirmed when it delivers one of the longest phase memory times ever recorded for a molecular two-qubit prototype.

Directed Self-Assembly, Symmetry Breaking, and Electronic Modulation of Metal Oxide Clusters by Pyramidal Heteroanions.

Mixed valence/metal polyoxometalate (POM) clusters are one of the most interesting host species because they show the ability to incorporate a wide range of heteroatoms of various charges and geometries. We report herein the incorporation of pyramidal EO32- heteroanions (E=PH, S, Se, Te) that are responsible not only for directing the templated assembly of a family of mixed-metal POMs but also for the symmetry-breaking of the traditional Dawson architecture and modulation of the electronic characteristics of the cluster's shell. The isolated family of POMs consists of four members: (Me2 NH2 )5 Na2 [Mo11 V7 O52 (HPO3 )]⋅MeOH⋅5 H2 O (1), (NH4 )7 [Mo11 V7 O52 (SO3 )]⋅12 H2 O (2), K7 [Mo11 V7 O52 (SeO3 )] ⋅31 H2 O (3), and (Me2 NH2 )6 Na[Mo11 V7 O52 (TeO3 )]⋅15 H2 O (4), and were characterized by X-ray structural analysis, electrospray ionization mass spectrometry (ESI-MS), thermogravimetric analysis (TGA), UV/Vis, FTIR, elemental analysis, flame atomic absorption spectroscopy (FAAS), and inductively coupled plasma optical emission spectroscopy (ICP-OES). Cyclic voltammetry (CV) and electron paramagnetic resonance (EPR) spectroscopic studies in concert with density functional theoretical (DFT) calculations have been used to elucidate the effect of the heteroatom on the electronic properties of the cluster.