Photo-Physical Transformations in Pyrazoline Derivative Based Systems

Abstract

Discovery of E/Z or trans-cis photoisomerization in the azobenzenes and their derivatives had the tremendous impact on the whole domain of photochromic materials including photochromic polymers and liquid crystals. Here we show similar configurational photoinduced transformation in a simple derivative of pyrazoline. The X-ray crystallographic investigations of (E)-3-(4-nitrostyryl)-1-phenyl-4,5-dihydro-1H-pyrazole (abbreviated as PYpNO 2 ) in grown crystals show two different structures comprising of either cis or trans molecules. The performed quantum chemical calculations confirm the existence of both configurations of PY-pNO 2 at the room temperature. Photophysical properties of this compound derived from quantum chemical calculations predict possibility of trans to cis switching of PY-pNO 2 by light. Indeed, molecules of PY-pNO 2 embedded in PMMA polymeric matrix when illuminated with 532 nm linearly polarized laser light show the induced optical anisotropy, i.e. birefringence characteristic for photoisomerizable molecules similar like in the group of the azobenzene derivatives.

All‐Optical Switching and Two‐States Light‐Controlled Coherent‐Incoherent Random Lasing in a Thiophene‐Based Donor‐Acceptor System

“…Based on this dependence it was possible to calculate the n 2 nonlinear optical refractive index equal to 3.0×10 −8 m 2 /W (1.6×10 −7 cm 2 /mW). This value is comparable or even higher to similar compounds e. g. based on the pyrazoline ring . Literature data confirmed high NLO capabilities of the investigated system and placed it among the other most efficient low‐molecular dyes, like azobenzene derivatives: CPND5 or S3 .…”

“…Comparing abovementioned organic system based on the pyrazoline derivative (PY‐ p NO 2 /PMMA) the 3 rd order nonlinear optical susceptibility tensor value for Th‐ p NO 2 /PMMA system is even higher about almost two orders of magnitude ( χ (3) for PY‐ p NO 2 /PMMA being equal to 5.6×10 −12 m 2 /V 2 ) . If we compare investigated compound – Th‐ p NO 2 , with the other well‐known organic nonlinear chromophore which characterizes excellent nonlinear optical features – i. e. DCNP molecule,, the χ (3) tensor value is again higher about one order of magnitude ( χ (3) for DCNP/PMMA is equal to 1.85×10 −11 m 2 /V 2 ) ,. In addition, the Kerr constant value defined for the investigated molecular system ( B for Th‐ p NO 2 /PMMA is equal to 3.6×10 −6 m/V 2 ) is about one order of magnitude higher than for abovementioned pyrazoline derivatives ( B =4.1×10 −7 m/V 2 and 3.9×10 −7 m/V 2 for the polymeric system doped with DCNP and PY‐ p NO 2 molecule, respectively).…”

“…The optical Kerr effect (OKE) phenomenon has been investigated in a typical pump‐probe experimental set‐up described elsewhere ,. In our case two cw lasers were used: the reference (He−Ne, λ=633 nm) and the pumping one (semiconductor GaN laser, λ=405 nm).…”

“…If we compare investigated compound – Th‐ p NO 2 , with the other well‐known organic nonlinear chromophore which characterizes excellent nonlinear optical features – i. e. DCNP molecule,, the χ (3) tensor value is again higher about one order of magnitude ( χ (3) for DCNP/PMMA is equal to 1.85×10 −11 m 2 /V 2 ) ,. In addition, the Kerr constant value defined for the investigated molecular system ( B for Th‐ p NO 2 /PMMA is equal to 3.6×10 −6 m/V 2 ) is about one order of magnitude higher than for abovementioned pyrazoline derivatives ( B =4.1×10 −7 m/V 2 and 3.9×10 −7 m/V 2 for the polymeric system doped with DCNP and PY‐ p NO 2 molecule, respectively). All the estimated nonlinear optical parameters are presented in Table .…”

“…To understand better the observed phenomena we decided to perform some calculations in the excited state with TD‐DFT methodology. However, the limitation of this approach is a common problem, in the literature we can find a number of examples that employs TD‐DFT/CAM‐B3LYP method which can qualitatively well describe many phenomena ,. In the first step we optimized the adiabatic geometries of all the isomers in their first singlet excited state and the obtained structures are displayed in Figure S1 in ESI.…”