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A bridging carbon analog of the well-studied bis(pyridyl)iminoisoindoline (BPI) can be produced via a one step reaction between diiminoisoindoline and pyridine-2-acetonitrile. The resultant bis(pyridineylidene)isoindoline (BPYI) is structurally analogous to BPI and can readily form metal complexes. However, it exhibits a markedly different electronic structure with intense absorption bands in the visible region of the spectrum.

Two sets of FeIII/II dithione complexes [FeII(iPr2Dt0)3][PF6]2 ([1][PF6]2), [FeII(Me2Dt0)3][PF6]2 ([2][PF6]2), and [FeIII(iPr2Dt0)3][PF6]3 ([3][PF6]3), [FeIII(Me2Dt0)3][PF6]3 ([4][PF6]3), and compound [FeIII(iPr2Dt0)3][FeCl4][PF]2 ([3][FeCl4][PF6]2) were synthesized from N,N′-diisopropyl piperazine-2,3-dithione (iPr2Dt0) and N,N′-dimethyl piperazine-2,3-dithione (Me2Dt0) ligands. Complexes [1][PF6]2–[4][PF6]3 have been characterized by NMR, IR, and UV-visible spectroscopies, and by electrochemistry. The molecular structures of [2][PF6]2 and [3][FeCl4][PF6]2 have been determined by X-ray crystallography. Complexes [2][PF6]2 and [3][FeCl4][PF6]2 both crystallized in the monoclinic space group P21/n. Both complexes exhibit distorted octahedral geometry and the three coordinated ligands in each complex exhibit different dithione folding. Complexes [1][PF6]2–[4][PF6]3 exhibit a single FeIII/II based couple and three quasi-reversible ligand-based redox couples. The electronic spectra of [1][PF6]2–[4][PF6]3 show intense MLCT bands that indicate strong mixing between metal and ligand orbitals. DFT calculations were used to provide a framework for understanding the electronic origin of their redox chemistry and spectroscopic features.

The hemiporphyrazine type chelate and phthalocyaninine analog biliazine (H2BlzH) and its metal complexes can be synthesized in one-step from a monosubstituted diiminisoindoline (DII). This singly substituted precursor is produced from the reaction of unsubstituted DII and 2-aminopyrazole. The biliazine macrocycle is a tetradentate chelate where the ring is closed via a strong hydrogen bond at the meso position. Although the hydrogen bond closes the ring, there is little evidence for 18-electron type annulene aromaticity across the macrocycle, as seen in the UV-visible and MCD spectra and supported by DFT calculations.

A ditriflate derivative of 2-iodoxybenzoic acid (IBX) was prepared by the reaction of IBX with trifluoromethanesulfonic acid and characterized by single crystal X-ray crystallography. IBX-ditriflate is the most powerful oxidant in a series of structurally similar IBX derivatives which is best illustrated by its ability to readily oxidize hydrocarbons and the oxidation resistant polyfluoroalcohols.

Phenol based aryliodonium salts were prepared by the reaction of [hydroxy(tosyloxy)iodo]arenes with aryl silyl ethers in the presence of trifluoromethanesulfonic acid. Structures of several aryliodonium salts with the hydroxy group in the para-position of the phenyl ring were established by single crystal X-ray crystallography. Under basic conditions, 4-hydroxyphenyl(phenyl)iodonium salts form a dimeric hypervalent iodine(iii) complex, oxyphenyl(phenyl)iodonium ylidic salt, the solid structure of which was confirmed by X-ray crystallography. Phenolic iodonium salts are potentially useful phenol transfer reagents in reactions with various anionic nucleophiles.

Several complexes of “PtL2” composition containing two cyanoxime anions – 2-oximino-2-cyano-N-piperidineacetamide (PiPCO−) and 2-oximino-2-cyano-N-morpholylacetamide (MCO−) – have been obtained and characterized both in solution and in the solid state. Complexes exist as two distinct polymorphs: monomeric yellow complexes and dark-green [PtL2]n 1D polymers, while for the MCO− anion a red, solvent containing dimeric [Pt(MCO)2·DMSO]2 complex has also been isolated. The interconversion of polymorphs was investigated. The monomeric PtL2 units are arranged into anisotropic extended solid [PtL2]n polymers with the help of Pt⋯Pt metallophilic interactions. Crystal structures of monomeric PtL2 (L = PiPCO−, MCO−) and red dimeric [Pt(MCO)2·DMSO]2 complexes were determined and revealed the cis-arrangement of cyanoxime anions. The Pt–Pt distance in the “head-to-tail” red dimer was found to be 3.133 A. The structure of the polymeric [Pt(PiPCO)2]n compound was elucidated using the EXAFS method and evidenced the formation of Pt-wires with ∼3.15 A intermetallic separation. The EPR spectra of both 1D polymers at variable temperatures indicate the absence of Pt(III) species. Both pure dark-green [PtL2]n polymers showed a considerable room temperature electrical conductivity of 20–30 S cm−1, which evidences the formation of a mixed valence Pt(II)/Pt(IV) system. We discovered that these 1D polymeric [PtL2]n complexes show an intense NIR fluorescence beyond 1000 nm, while yellow monomeric PtL2 complexes are not emissive at all. The room temperature excitation spectra of 1D polymeric [PtL2]n complexes demonstrated their strong emission beyond 1000 nm regardless of the used excitation wavelength between 350 and 800 nm, which is typical of systems with delocalized charge carriers. For the first time the formation of mixed valence “metal wires” held together by metallophilic interactions is directly linked both with an intense fluorescence in the NIR region of the spectrum and with the electrical conductivity. The effect of the concentration of [PtL2]n complexes dispersed in the dielectric salt matrix on the photoluminescence wavelength and intensity was investigated. Both polymers show a quantum yield that is remarkably high for this region of the spectrum, reaching ∼2%. Variable temperature emission of polymeric [PtL2]n in the −190–+60 °C range was studied as well.

A large variety of conceptual three- and fourfold tetraazaporphyrin- and subtetraazaporphyrin-based functional 3D nanocage and nanobarrel structures have been proposed on the basis of in silico design. The designed structures differ in their sizes, topology, porosity, and conjugation properties. The stability of nanocages of Oh symmetry and nanobarrels of D4h symmetry was revealed on the basis of DFT and MD calculations, whereas their optical properties were assessed using a TDDFT approach and a long-range corrected LC-wPBE exchange-correlation functional. It was shown that the electronic structures and vertical excitation energies of the functional nanocage and nanobarrel structures could be easily tuned via their size, topology, and the presence of bridging sp(3) carbon atoms. TDDFT calculations suggest significantly lower excitation energies in fully conjugated nanocages and nanobarrels compared with systems with bridging sp(3) carbon fragments. Based on DFT and TDDFT calculations, the optical properties of the new materials can rival those of known quantum dots and are superior to those of monomeric phthalocyanines and their analogues. The methane gas adsorption properties of the new nanostructures and nanotubes generated by conversion from nanobarrels were studied using an MD simulation approach. The ability to store large quantities of methane (106-216 cm(3) (STP) cm(-3)) was observed in all cases with several compounds being close to or exceeding the DOE target of 180 cm(3) (STP) cm(-3) for material-based methane storage at a pressure of 3.5 MPa and room temperature.

Dimeric metal complexes can often exhibit coupling interactions via bridging ligands. In this report, we present two Re(CO)3 dimers, where the metals are linked via a bis(pyca) hydrazine (pyca = pyridine-2-carbaldehyde imine) Schiff base ligand. For the dimeric compounds 4 and 5, we observe strong coupling across the dimer as measured by cyclic voltammetry: ∼480 mV separations between the first and the second reduction waves that correspond to comproportionation constants close to 1.5 × 10(8). Evidence for a mixed valence state upon one electron reduction was also observed by spectroelectrochemistry in which a clear inter-valence charge-transfer (IVCT) band was observed in [4]- and [5]-complexes. The electronic structures of all target compounds were probed by DFT and TDDFT computational methods. DFT calculations indicate that reduction takes place at the diimine units, and that the observed coupling is a ligand-based phenomenon, rather than one that involves metal-based orbitals.

A new pseudocyclic triflate derivative of benziodoxole (IBA-OTf) was prepared and characterized by X-ray analysis. This highly electrophilic reagent readily reacts with various organic substrates to give the corresponding products in good yields. Furthermore, IBA-OTf can be used as a catalyst with m-chloroperoxybenzoic acid as the terminal oxidant.

The oxygen atom transfer reactivity (OAT) of dioxo-Mo(VI) complexes of hydrotrispyrazolyl borate (hydrotris(3,5-dimethylpyrazolyl)borate, Tp(Me2); hydrotris(3-isopropylpyrazol-1-yl)borate, Tp(iPr)) with tertiary phosphines (PMe(3), PMe(2)Ph, PEt(3), PEt(2)Ph, PBu(n)(3), PMePh(2), or PEtPh(2)) has been investigated. In acetonitrile, these reactions proceed via the formation of a phosphoryl intermediate complex that undergoes a solvolysis reaction. We report the synthesis and characterization of several phosphoryl complexes. The rates of formation of phosphoryl complexes and their solvation were determined by spectrophotometry. The rates of the reactions and the properties of the phosphoryl species were investigated using the Quantitative Analysis of Ligand Effect (QALE) methodology. The results show that, at least in this system, the first step of the reaction is controlled primarily by the steric factor, and in the second step, both electronic and steric factors are important. We also analyzed the effect of ligands on the reaction rate i.e., Tp(Me2)vs. Tp(iPr).

A series of bisaxially co-ordinated low-spin iron(II) phthalocyanine complexes (pc)FeL2 with different types of nitrogen bases as axial ligands has been prepared and characterised by electronic, 1H NMR and Mossbauer spectroscopies. The influence of electronic and steric effects of the axial ligands on Mossbauer quadrupole splitting (ΔEQ) and isomer shift (δ), NMR parameters, and metal-to-ligand charge transfer (MLCT) band position are discussed. Mossbauer partial quadrupole splitting (p.q.s.) and partial isomer shift (p.i.s.) parameters for different ligands have been estimated and rationalised with the overall data for (pc)FeL2 and (nx)2FeL2 (nx = nioxime) complexes. A semi-empirical AM1 method and the cone angle concept were used to factorise σ- and π-electronic and steric effects of the ligands. A good correlation between the predicted and experimental MLCT band position of (pc)FeL1L2 complexes, as well as predicted and experimental p.i.s. and p.q.s. values for different ligands, has been observed.

The mixed-ligand phthalocyanine lanthanide complexes [Ln(pc)X2] [pc = phthalocyanine radical anion; Ln = Sm, Eu, Gd or Lu; X = 1,1,1,2,2,3,3-heptafluoro-7,7-dimethyloctane-4,6-dionate (fod), 1,1,1-trifluoro-4-phenylbutane-2,4-dionate (btfa) or 3-heptafluorobutyryl-D-camphorate (hfbc)] have been synthesized and characterized by electronic, ESR and plasma desorption mass spectroscopy as well as elemental analysis. Bands in the electronic spectra at 820, 716, 500, 425 and 330 nm typical for phthalocyanine radical anions have been observed for the red initial [Ln(pc)X2] complexes. The ESR spectra are also consistent with the radical nature of the phthalocyanine ligand in these complexes. The reversible chemical reduction of [Ln(pc)X2] complexes has been studied.

The A-ring oxidation/contraction of 3-oxotriterpenoids was developed as a two-step and “one pot” process. A benzylic acid type rearrangement of triterpenoid diosphenols gives (S)- as major and (R)-α-hydroxycarboxylic acids as minor reaction products. The absolute configurations were determined from the X-ray crystal structure analysis. The mechanism of ring contraction was modelled computationally at the DFT and MP2 levels of theory. The tautomeric triterpenoid A-seco δ-oxocarboxylic acids and A-ring hydroxy lactones formed after deep oxidation/acidification of 3-oxotriterpenoids.

Absorption spectra of several free base triarylcorroles were investigated by MCD spectroscopy. The MCD spectra exhibit unusual sign-reverse (positive-to-negative intensities in ascending energy) features in the Soret- and Q-type band regions, suggesting a rare ΔHOMO < ΔLUMO relationship between π and π* MOs in the corrole core.

Crystal structures of potassium, rubidium, and cesium triphenylcyanoborates were investigated in order to explain high selectivity of triphenylcyanoborate ion (“caesignost”) as an agent for cesium precipitation. Alkali metal ions have substantially different coordination modes with triphenylcyanoborate ion coordinated to the cyano group in the end-on or side-on motif and to the phenyl group in the π–M+ motif.

Redox properties of several transition-metal MTFcP complexes (TFcP2− = 5,10,15,20-tetraferrocenylporphyrin, M = Co2+, Ni2+, Cu2+, and Zn2+) were investigated using electrochemical (CV and DPV), spectroelectrochemical, and chemical oxidation approaches. Electrochemical experiments conducted in a low-polarity solvent using a non-coordinating electrolyte are crucial for the sequential oxidation of ferrocene substituents along with porphyrin-based single-electron oxidation and reduction processes. The first ferrocene oxidation process in all MTFcP complexes is separated by at least 140 mV from the next three ferrocene based oxidations. The second, third, and fourth redox processes in the ferrocene region are more closely spaced, with the largest separation observed in CuTFcP and CoTFcP complexes. Mixed-valence compounds were observed and characterized by spectroelectrochemical and chemical oxidation approaches. In all cases, intervalence charge transfer (IVCT) bands were detected confirming the existence of the iron-based mixed-valence [MTFcP]n+ (n = 1–3) species and suggesting long-range metal–metal coupling in the target systems. The resulting data from the mixed-valence [MTFcP]n+ (n = 1–3) complexes matched very closely to the metal-free poly(ferrocenyl)porphyrins previously reported and were assigned as Robin and Day Class II mixed-valence compounds. In the case of CoTFcP, the selective oxidation of a central metal was also demonstrated in the presence of the strong ligand-field anions using oxygen as an oxidant.

A tetraazaporphyrin (TAP) prepared by condensation of 1-ferrocenyl-1,2,2-tricyanoethylene in the presence of magnesium shows an intense, broad near-IR band in the 700–1300 nm region, which may be ascribed to charge-transfer transitions from the ferrocenyl moiety (substituents) to the TAP ligand.

Single crystal X-ray structures of two 2-iodylbenzenesulfonamides reveal a combination of intra- and intermolecular I⋯O interactions leading to a typical hexacoordinated and a unique heptacoordinated iodine(V) center.

A stable molybdenum(V) complex, LMoOCl2 (where L is hydrotris(3,5-dimethylpyrazolyl)borate), has been oxidized under mass spectrometric conditions. The oxidized species reacts with tertiary phosphines and the products have been detected by mass spectrometry. The product distribution has been followed by isotope labeling experiments, and energy dependent electrospray mass spectrometry. These experiments reveal not only oxygen atom transfer but also loss of a chlorine atom from the resulting species.

A large number of para-substituted benzene thiols and the corresponding disulfides were synthesized and characterized by 1H NMR, 13C NMR, and IR spectroscopies. Geometries of all sixteen thiols and fourteen disulfide compounds were optimized at the B3LYP/6-31G(d) level, while the electronic structure and the 13C isotropic shifts were calculated by ab initio Hartree-Fock method coupled with the Gauge-Independent Atomic Orbital (GIAO) algorithm and a 6-31+G(d,p) basis set. The calculated 13C NMR isotropic shifts exhibit admirable agreement (δ rmsd ∼4.6 ppm) with the experimental data. The chemical shift of para-substituted carbon showed a linear correlation with Hammett constants (σp and σp+). Using this methodology the σp+ constants for the dendritic ligands have been estimated to be 0.25 and 0.24 for 2(n) and 2(o), respectively. In addition, the NBO charges on the sulfur atoms shows a latent response with the σp+ parameter. The atomic charge on the thiophenolato sulfur is invariant with the electron withdrawing ability of the substituents, however, the charge increases with increasing electron-withdrawing power.