An azobenzene based
iminopyridine ligand 1 has been synthesized by a condensation
reaction between N,N-dimethyl-4,4′-azodianiline
and 2-formylpyridine. The complexation of the ligand with ZnCl2 afforded a tetrahedral neutral zinc metal complex (2) formulated as [(Azo-Imino-Py)ZnCl2]. The crystal
structure analysis of the complex indicates the formation of a tetracoordinated
zinc(II) ion with the expected tetrahedral geometry. In solid state,
a 2D supramolecular architecture reinforced by π–π
stacking and hydrogen bonding is observed. The UV–visible spectrophotometric
titration studies of the ligand, by increasing amount of ZnCl2, confirm the existence of single complex species in solution.
The nonlinear optical (NLO) investigations by Z-scan technique of
both ligand 1 and complex 2 indicate a dramatic
enhancement of the NLO absorption of the ligand upon complexation
with ZnCl2. This enhancement is likely to be due to a large
dipole moment found for the complex 2 as calculated by
DFT/B3LYP methodology.
We describe herein the synthesis and characterization of a thiophene-based donor-acceptor system, namely (E)-2-(4-nitrostyryl)-5-phenylthiophene (Th-pNO ), which was prepared under Horner-Wadsworth-Emmons conditions. The UV/Vis absorption bands, including the intramolecular charge transfer (ICT) band, were fully assigned using DFT and TD-DFT computations. The results of both efficient third-order nonlinear optical properties and light-amplification phenomena are presented. Investigations of photoinduced birefringence (PIB) in optical Kerr effect (OKE) experiments showed a great potential for this particular compound as an efficient, fully reversible, and fast optical switch. Time constants for the observed trans-cis-trans molecular transitions are in the range of microseconds and give a competitive experimental result for the well-known and exploited azobenzene derivatives. Random lasing (RL) investigations confirmed that this organic system is potentially useful to achieve strong light enhancement, observed as a multimode lasing action. Both RL and OKE measurements indicate that this material is a representative of thiophene derivatives, which can be utilized to fabricate fast all-optical switches or random lasers (light amplifiers).
Cocrystallization
of 7,7′,8,8′-tetracyanoquinodimethane
radical anion (TCNQ–•) and 3-methylpyridinium-1,2,3,5-dithiadiazolyl
radical cation (3-MepyDTDA+•) afforded isostructural
acetonitrile (MeCN) or propionitrile (EtCN) solvates containing cofacial
π dimers of homologous components. Loss of lattice solvent from
the diamagnetic solvates above 366 K affords a high-temperature paramagnetic
phase containing discrete TCNQ–• and weakly
bound π dimers of 3-MepyDTDA+•, as evidenced
by X-ray diffraction methods and magnetic susceptibility measurements.
Below 268 K, a first-order phase transition occurs, leading to a low-temperature
diamagnetic phase with TCNQ–• σ dimer
and π dimers of 3-MepyDTDA+•. This study reveals
the first example of cooperative interactions between two different
organic radical ions leading to magnetic bistability, and these results
are central to the future design of multicomponent functional molecular
materials.
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Highlights Two rhenium metal complexes have been prepared and structurally characterized Absorption spectra have been measured DFT calculations have been performed to support the experimental results Photoisomerization studies of the azo group in the ligands and in the metal complexes have been performed.
AbstractThe reaction of rhenium(I) pentacarbonyl chloride Re (CO)5Cl with N,N-dimethyl-4-((E)-(pyridin-2ylmethylene) amino)phenyl) diazenyl) aniline L1 and (E)-4-((E)-(4-nitrophenyl)diazenyl)-N-(pyridin-2ylmethylene) aniline L2 affords two rhenium metal complexes [ReL1(CO)3Cl] (ReL1) and [ReL2(CO)3Cl] (ReL2) , respectively. These Re(I) complexes were characterized in detail, including their single crystal structures, absorption spectra and electronic structures using DFT calculations. Trans to cis photoisomerization of the free ligands and complexes was investigated experimentally and rationalized theoretically. Interestingly, light-induced photoisomerization of the azo fragment is observed for free ligand L1 while inhibition of this process is produced upon coordination to Re metal cation.
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