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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.

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.

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 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.

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.