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archives@tulane.edu / This dissertation is dedicated to the study of the synthesis, crystal structures, properties, and reactivity of heteroleptic metallodithiolene complexes of the Group 10 metals. In this work, we report a systematic survey of the reactivity of [(Ph2C2S2)2M] (M = Ni, Pd, Pt) toward ligand substitution. The upshots of the survey are the clarification of the attributes of the incoming ligand that facilitate ligand displacement, creation of a new set of heteroleptic dithiolene complexes, [M(Ph2C2S2)(C≡NR)2] (M = Ni, Pd, Pt; R = Me, Bn, Cy, tBu, 1-Adamantyl, Ph), and improvement in the efficiency by which mixed-ligand “push-pull” compounds are made. The scope of dithiolene ligand displacement by incoming ligands was expanded beyond the already reported phosphine and diimine ligands. Spectroscopic and physical characterization techniques including S K-edge X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) were used in conjunction with DFT computational methods to establish the properties of the compounds prepared in this study. Representative [(Ph2C2S2)Pt(C≡NR)2] (R = aryl) complexes exihibited low temperature luminscence in frozen solvent glasses with relatively long lifetimes. The relevance of the dithiolene redox non-innocence in the ligand substitution mechanism has also been elucidated, thereby giving an insight into the fate of the displaced dithiolene ligand. Redox disproportionation between two radical monoanionic dithiolene ligands leads to the creation of a dithione, which is an enhanced leaving group and an inherently reactive species. When displacement of dithiolene ligand from [(Ph2C2S2)2Ni] was conducted with a twofold excess of C≡NCy, 4,5-diphenyl-1,3-dithiol-2-cyclohexylimine could be isolated. The identification and characterization of this compound is consistent with the creation of dithiobenzil during the ligand substitution. The reactive α-dithione is also capable of undergoing rapid irreversible polymerization, thereby providing the thermodynamic impetus for the dithiolene ligand substitution. Chemical oxidation of [Pt(Ph2C2S2)(C≡NtBu)2] with [N(C6H4Br-4)3][SbCl6] was undertaken to form [Pt(Ph2C2SˉS‧)(C≡NtBu)2]2[SbCl6]2. Structural determination of the dication revealed appreciable shortening and lengthening of C─S and C─C bond distances, respectively, within the dithiolene ligand as compared to the charge-neutral complex, an observation which confirmed the dithiolene ligand as the locus of the redox activity in the heteroleptic monodithiolene complexes. The utility of [M(Ph2C2S2)(C≡NMe)2] (M= Ni, Pd, Pt) as synthons in their own right for heteroleptic compounds not directly attainable by ligand substitution from [M(Ph2C2S2)2] was also explored. The panorama of outcomes when [M(S2C2Ph2)(CNMe)2] (M = Ni2+, Pd2+, Pt2+) are introduced to new ligands intended to substitute for CNMe has been thoroughly defined. The most significant breakthrough was the isolation of the dicyanide complex, [Et4N]2[Ni(S2C2Ph2)(C≡N)2], which is a potentially useful precursor toward cyanide-bridged multimetallic architectures. Finally, the synthesis and structural characterization of multimetallic complexes bridged by bis(diphenylphosphine) ligands and redox active dithiolenes as end capping ligands are described. The electrochemistry study revealed that the dimetallic compounds support reversible oxidation to dications, which likely have singlet diradical - triplet states in close equilibrium. The use of dithiolene ligands as electron spin hosts offers new possibilities for the application of metallodithiolene complexes in molecule-based spintronic devices, such as quantum bits (qubits). / 1 / Antony Obanda

This research focused on the development of new metal triimine complexes of Pt(II), Pd(II), and Ni(II) for use in three types of molecular electronic devices: dye sensitized solar cells (DSSCs), organic light-emitting diodes (OLEDs), and organic field effect transistors (OFETs). Inorganic complexes combine many advantages of their chemical and photophysical properties and are processable on inexpensive and large area substrates for various optoelectronic applications. For DSSCs, a series of platinum (II) triimine complexes were synthesized and evaluated as dyes for nanocrystalline oxide semiconductors. Pt (II) forms four coordinate square planar complexes with various co-ligands and counterions and leads to spanning absorption across a wide range in the UV-Vis-NIR regions. When those compounds were applied to the oxide semiconductors, they led to photocurrent generation thus verifying the concept of their utility in solar cells. In the OLEDs project, a novel pyridyl-triazolate Pt(II) complex, Pt(ptp)2 was synthesized and generated breakthrough OLEDs. In the solution state, the electronic absorption and emission of the square planar structure results in metal-to-ligand charge transfer (MLCT) and an aggregation band. Tunable photoluminescence and electroluminescence colors from blue to red wavelengths have been attained upon using Pt(ptp)2 under different experimental conditions and OLED architectures. In taking advantage of these binary characteristics for both monomer and excimer emissions, cool and warm white OLEDs suitable for solid-state lighting have been fabricated. The OFETs project represented an extension of the study of pyridyl-triazolate d8 metal complexes due to their electron-transporting behavior and n-type properties. A prescreening step by using thermogravimetric calorimetry has demonstrated the stability of all three M(ptp)2 and M(ptp)2(py)2 compounds and their amenability to sublimation. Preliminary current-voltage measurements from simple diodes has achieved unidirectional current from a Pt(ptp)2 neat layer and demonstrated its n-type semiconducting behavior.

Our group has been developing normal CCC-NHC pincer complexes for catalysis and OLED applications. However, synthesizing the abnormal analogs has been challenging due to the difficulty in accessing the ligand precursors. This study addresses these challenges, marking a significant step in CCC-NHC pincer chemistry. The abnormal CCC-NHC proligands were synthesized through Ullmann-type coupling of 2-phenylimidazole to 1,3-dibromobenzene. The intermediate 1,3-bis(2-phenylimidazole)benzene was alkylated with 1-iodobutane to obtain the 1,3-bis(N-butyl-2-phenylimidazole)benzene diiodide salt. The proligands 1,3-bis(N-butyl-2-phenylimidazole)benzene dichloride/diiodide were metalated with [Zr(NMe2)4] and transmetalated to group 10 metals (Ni, Pd, Pt) using [NiCl2(glyme)], [Pd(COD)Cl2], and [Pt(COD)Cl2]. Electrospray ionization of the CCC-aNHC pincer complexes [(BuCa-iCa-iCBu)MX] (M = Ni, Pd, Pt, X = Cl, I) in acetonitrile generated dinitrogen adducts [(BuCa-iCa-iCBu)M-N2]+, representing a rare example of group 10 dinitrogen complexes. The coordination of N2 to the cationic species means the pincer ligand provides the required electron density to the metals to stabilize the N2 through π-backbonding. The redox chemistry of NiII and PdII complexes bearing the super electron donating CCC-aNHC pincer ligand was investigated. The PdII complexes were cleanly oxidized with two electron oxidants, such as iodobenzene dichloride (PhICl2). The oxidation of the PdII complex with a half equiv of the oxidants gave mixed valent PdII/PdIV dimer as a thermodynamically preferred product. The oxidation of the CCC-aNHC NiII chloride complex with PhCl2 produced unstable NiIII species. However, utilizing anhydrous CuCl2 as the oxidant yielded a bis-ligated NiIV complex, a seemingly common occurrence among the first-row metals (Fe and Co). Emissive square planar Pt complexes have been utilized to produce OLEDs, but those with halides pose potential threats due to the electrochemical instability of halide complexes. Thus, it is highly desirable that halide-free square planar Pt complexes that maintain high molecular rigidity are developed. The CCC-aNHC pincer Pt halide complexes were emissive when irradiated with UV light. The pincer Pt halide complexes were converted to Pt azolate complexes and retained their emission properties. Substituting halides on Pt complexes with azolates increases the PLQY from 7 % to 24 % and the emission lifetimes from 1.0 μs to 1.4 μs in the solid states.