Bay-Extended, Distorted Perylene Esters Showing Visible Luminescence after Ultraviolet Excitation: Photophysical and Electrochemical Analysis

Perylene derivatives with a unilaterally and bilaterally extended core show luminescence in the visible wavelength range (500–600 nm) that can be excited by absorption in the ultraviolet range (360–370 nm). This unusual behavior is investigated by means of excitation spectroscopy, cyclic voltammetry, and calculations based on (time-dependent) density functional theory. The results indicate that the extended compounds show promising features for optoelectronic applications and even might be used as fluorescent dyes in lasing. This is supported by nonadiabatic ab initio molecular dynamics. With respect to applications in organic optoelectronic nanostructures, nanofilms were prepared via spin-coating and thermal vapor deposition and demonstrated the formation of excimers. The relationship between the excimer-induced bathochromic shift and the interplanar distance of the molecules opens up the possibility to vary the perceived color of a nanofilm via tempering

Cyclopentadienide Ligand Cp^C– Possessing Intrinsic Helical Chirality and Its Ferrocene Analogues

The novel chiral cyclopentadiene-type ligand Cp^CH is accessible from dibenzosuberenone in a five-step sequence with overall yields of 64%. NMR spectroscopy as well as DFT calculations prove that the racemization of this compound is slow at room temperature. By deprotonation of Cp^CH and subsequent reaction with appropriate iron­(II) precursors, the novel ferrocene derivatives (Cp^C)₂Fe and (Cp^C)­Fe­(⁴Cp) are accessible in good yields. The latter could structurally be characterized by means of single-crystal X-ray crystallography. Mössbauer spectroscopy proves the ferrocene nature of (Cp^C)₂Fe and (Cp^C)­Fe­(⁴Cp), and electrochemical investigations carried out with (Cp^C)­Fe­(⁴Cp) show that the compound is, as expected, more easily oxidized than ferrocene

Cyclopentadienide Ligand Cp^C– Possessing Intrinsic Helical Chirality and Its Ferrocene Analogues

The novel chiral cyclopentadiene-type ligand Cp^CH is accessible from dibenzosuberenone in a five-step sequence with overall yields of 64%. NMR spectroscopy as well as DFT calculations prove that the racemization of this compound is slow at room temperature. By deprotonation of Cp^CH and subsequent reaction with appropriate iron­(II) precursors, the novel ferrocene derivatives (Cp^C)₂Fe and (Cp^C)­Fe­(⁴Cp) are accessible in good yields. The latter could structurally be characterized by means of single-crystal X-ray crystallography. Mössbauer spectroscopy proves the ferrocene nature of (Cp^C)₂Fe and (Cp^C)­Fe­(⁴Cp), and electrochemical investigations carried out with (Cp^C)­Fe­(⁴Cp) show that the compound is, as expected, more easily oxidized than ferrocene

Cyclopentadienide Ligand Cp^C– Possessing Intrinsic Helical Chirality and Its Ferrocene Analogues

The novel chiral cyclopentadiene-type ligand Cp^CH is accessible from dibenzosuberenone in a five-step sequence with overall yields of 64%. NMR spectroscopy as well as DFT calculations prove that the racemization of this compound is slow at room temperature. By deprotonation of Cp^CH and subsequent reaction with appropriate iron­(II) precursors, the novel ferrocene derivatives (Cp^C)₂Fe and (Cp^C)­Fe­(⁴Cp) are accessible in good yields. The latter could structurally be characterized by means of single-crystal X-ray crystallography. Mössbauer spectroscopy proves the ferrocene nature of (Cp^C)₂Fe and (Cp^C)­Fe­(⁴Cp), and electrochemical investigations carried out with (Cp^C)­Fe­(⁴Cp) show that the compound is, as expected, more easily oxidized than ferrocene

Cyclopentadienide Ligand Cp^C– Possessing Intrinsic Helical Chirality and Its Ferrocene Analogues

The novel chiral cyclopentadiene-type ligand Cp^CH is accessible from dibenzosuberenone in a five-step sequence with overall yields of 64%. NMR spectroscopy as well as DFT calculations prove that the racemization of this compound is slow at room temperature. By deprotonation of Cp^CH and subsequent reaction with appropriate iron­(II) precursors, the novel ferrocene derivatives (Cp^C)₂Fe and (Cp^C)­Fe­(⁴Cp) are accessible in good yields. The latter could structurally be characterized by means of single-crystal X-ray crystallography. Mössbauer spectroscopy proves the ferrocene nature of (Cp^C)₂Fe and (Cp^C)­Fe­(⁴Cp), and electrochemical investigations carried out with (Cp^C)­Fe­(⁴Cp) show that the compound is, as expected, more easily oxidized than ferrocene

The Connection between NHC Ligand Count and Photophysical Properties in Fe(II) Photosensitizers: An Experimental Study

Four homo- and heteroleptic complexes bearing both polypyridyl units and N-heterocyclic carbene (NHC) donor functions are studied as potential noble metal-free photosensitizers. The complexes [Fe^II(L1)­(terpy)]­[PF₆]₂, [Fe^II(L2)₂]­[PF₆]₂, [Fe^II(L1)­(L3)]­[PF₆]₂, and [Fe^II(L3)₂]­[PF₆]₂ (terpy = 2,2′:6′,2″ terpyridine, L1 = 2,6-bis­[3-(2,6-diisopropylphenyl)­imidazol-2-ylidene]­pyridine, L2 = 2,6-bis­[3-isopropylimidazol-2-ylidene]­pyridine, L3 = 1-(2,2′-bipyridyl)-3-methylimidazol-2-ylidene) contain tridentate ligands of the C^N^C and N^N^C type, respectively, resulting in a Fe-NHC number between two and four. Thorough ground state characterization by single crystal diffraction, electrochemistry, valence-to-core X-ray emission spectroscopy (VtC-XES), and high energy resolution fluorescence detected X-ray absorption near edge structure (HERFD-XANES) in combination with ab initio calculations show a correlation between the geometric and electronic structure of these new compounds and the number of the NHC donor functions. These results serve as a basis for the investigation of the excited states by ultrafast transient absorption spectroscopy, where the lifetime of the ³MLCT states is found to increase with the NHC donor count. The results demonstrate for the first time the close interplay between the number of NHC functionalities in Fe­(II) complexes and their photochemical properties, as revealed in a comparison of the activity as photosensitizers in photocatalytic proton reduction