2569-55-3

Upstream product

• 462-08-8 pyridin-3-ylamine 
• 586-96-9 Nitrosobenzene 
• 2569-55-3 3-(phenyldiazenyl)pyridine 

Downstream Products

• 17999-52-9 1-phenyl-2-(3-pyridyl)hydrazine 
• 2569-62-2 3-(phenyl-α-azoxy)pyridine-N-oxide 
• 103987-63-9 3-(2,4-dibromo-phenyl-trans-azo)-pyridine 
• 2569-55-3 3-(phenyldiazenyl)pyridine 
• 6759-49-5 4-(2-(pyridin-3-yl)diazenyl)phenol 
• 93830-71-8 3-(phenyl-β-azoxy)pyridine-N-oxide 

Relevant academic research and scientific papers

FeIII spin-crossover complexes with photoisomerizable ligands: Experimental and theoretical studies on the ligand-driven light-induced spin change effect

Conflicting results have been reported with respect to the photoinduced switching of the magnetic properties of [FeIII(salten)]+ complexes [salten = 4-azaheptamethylene-1,7-bis(salicylideneiminate)] coordinated by photoisomerizable ligands. In order to address this problem, two FeIII complexes [Fe(salten)(3-azpy)]BPh4 (1) and [Fe(salten)(4-azpy)]BPh4 (2) have been synthesized and characterized by various physicochemical methods (azpy = phenylazopyridine). Both 1 and 2 exhibit a low spin (S = 1/2) to high spin (HS, S = 5/2) transition in the solid state. In solution at room temperature both complexes are predominantly HS. Upon exposure to 310 (trans → cis) and 440 nm radiation (cis → trans) the free and coordinated 3- and 4-azpy ligands undergo a reversible cis-trans isomerization. For 2 a corresponding reduction of the HS fraction 2% is observed, whereas in 1 no effect is observed. Extensive DFT calculations, which employ different functionals and basis sets, explain this experimental result. The consequences of these findings with respect to the design of spin-switchable iron(III) complexes with photoactive ligands are discussed.

Thermal spin crossover behaviour of two-dimensional hofmann-type coordination polymers incorporating photoactive ligands

Two spin crossover (SCO)-active 2D Hofmann-type framework materials, [Fe(3-PAP)2Pd(CN)4] (A) and [Fe(4-PAP)2 Pd(CN)4] (B) containing the photoactive azo-benzene-type ligands 3-phenylazo-pyridine (3-PAP) and 4-phenylazopyridine (4-PAP) were prepared. These materials form non-porous Hofmann-type structures whereby 2D [FeIIPd(CN)4] grids are separated by 3- or 4-PAP ligands. The iron(II) sites of both materials (A and B) undergo abrupt and hysteretic spin transitions with characteristic transition temperatures T1/2↓,↑: 178, 190K (ΔT: 12K) and T1/2↓,↑: 233, 250K (ΔT: 17 K), respectively. Photo-magnetic characterisations reveal light-induced excited spin state trapping (LIESST) activity in both A and B with characteristic T(LIESST) values of 45 and 40 K. Although both free ligands show trans- to-cis isomerisation in solution under UV-irradiation, as evidenced via absorption spectroscopy, such photo-activity was not observed in the ligands or complexes A and B in the solid state. Structural analysis of a further non-SCO active isomer to B, [Fe(4-PAP)2 Pd(CN)4]·1/2(4-PAP) (B·(4-PAP)), which contains free ligand in the pore space is reported.

Synthesis and Photophysical Characterization of Azoheteroarenes

A set of azoheteroarenes have been synthesized with Buchwald-Hartwig coupling and microwave-assisted O2 oxidation as the key steps. Several compounds exhibit good to excellent photoswitching properties (high switching efficiency, good fatigue r

Light-driven coordination-induced spin-state switching: Rational design of photodissociable ligands

The bistability of spin states (e.g., spin crossover) in bulk materials is well investigated and understood. We recently extended spin-state switching to isolated molecules at room temperature (light-driven coordination-induced spin-state switching, or LD-CISSS). Whereas bistability and hysteresis in conventional spin-crossover materials are caused by cooperative effects in the crystal lattice, spin switching in LD-CISSS is achieved by reversibly changing the coordination number of a metal complex by means of a photochromic ligand that binds in one configuration but dissociates in the other form. We present mathematical proof that the maximum efficiency in property switching by such a photodissociable ligand (PDL) is only dependent on the ratio of the association constants of both configurations. Rational design by using DFT calculations was applied to develop a photoswitchable ligand with a high switching efficiency. The starting point was a nickel-porphyrin as the transition-metal complex and 3-phenylazopyridine as the photodissociable ligand. Calculations and experiments were performed in two iterative steps to find a substitution pattern at the phenylazopyridine ligand that provided optimum performance. Following this strategy, we synthesized an improved photodissociable ligand that binds to the Ni-porphyrin with an association constant that is 5.36times higher in its trans form than in the cis form. The switching efficiency between the diamagnetic and paramagnetic state is efficient as well (72 % paramagnetic Ni-porphyrin after irradiation at 365nm, 32 % paramagnetic species after irradiation at 440nm). Potential applications arise from the fact that the LD-CISSS approach for the first time allows reversible switching of the magnetic susceptibility of a homogeneous solution. Photoswitchable contrast agents for magnetic resonance imaging and light-controlled magnetic levitation are conceivable applications. Turn the spin: Nickel-porphyrins with appropriately designed axial photochromic ligands change their coordination number and consequently their spin state reversibly upon irradiation. Rational design led to a substituted 3-phenylazopyridine as a photodissociable ligand with a switching efficiency of 40 % (see figure). Thus, the magnetic susceptibility of a homogeneous solution was switched by a factor of more than two at room temperature.

Acid-catalysed aryl hydroxylation of phenylazopyridines: Reaction intermediates, kinetics and mechanism

A kinetic and product analysis study of the reactions of the three isomeric phenylazopyridines (PAPys) in aqueous sulfuric acid media (30-97 wt% H2SO4) is reported. The final products obtained from the reaction of 4-(phenylazo)pyridine (4-PAPy) are the hydroxylated product 4-(4-hydroxyphenylazo)pyridine, the reduction products 4-aminophenol and 4-aminopyridine, and a small amount of a dimerized product. 3-(Phenylazo)pyridine is unreactive, but 2-(phenylazo)pyridine gives the equivalent 2-(4-hydroxyphenylazo)pyridine, 4-aminophenol and 2-aminopyridine products. This product pattern, an oxidized azo-compound and two reduced amines, is similar to that found in the disproportionation of di-p-substituted hydrazinobenzenes observed in benzidine rearrangement studies. Consequently it has been proposed that the corresponding [N′-(4-hydroxyphenylhydrazino)]pyridines were formed as reaction intermediates in the present system; this is confirmed by showing that [N′-4-(4-hydroxyphenylhydrazino)-pyridine synthesized independently gave the same products as 4-PAPy under the same conditions. The kinetic study shows that the 4-isomer reacted faster than the 2-isomer at all the acid concentrations investigated (the 3-isomer being inert). Rate maxima are observed, at ～72 wt% H2SO4 for 4-PAPy and ～86 wt% H2SO4 for 2-PAPy. To facilitate the kinetic analysis, values of pKBH22+ for the protonation of the substrates and the possible hydroxy products at the azo-group were determined, using the excess acidity method; the first protonation occurs on the pyridine nitrogen in the pH region. An excess acidity analysis of the observed pseudo-first-order rate constants as a function of acidity indicate an A2 mechanism, with the diprotonated substrate and either one HSO4- ion or one H2O molecule in the activated complex. The proposed mechanism thus involves nucleophilic attack of HSO4- or H2O at an aryl carbon of the diprotonated substrate in the slow step, resulting in an intermediate hydrazo species which gives the observed products in a subsequent fast step (cf. benzidine rearrangement).