: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Solid state emitters based on excited state intramolecular proton transfer (ESIPT) have been attracting considerable interest since the past few years in the field of optoelectronic devices because of their desirable unique photophysical properties. The photophysical properties of the solid state ESIPT fluorophores determine their possible applicability in functional materials. Less fluorescence quantum efficiencies and short fluorescence lifetime in the solid state are the shortcomings of the existing ESIPT solid state emitters. Designing of ESIPT chromophores with high fluorescence quantum efficiencies and a long fluorescence lifetime in the solid state is a challenging issue because of the unclear mechanism of the solid state emitters in the excited state. Reported design strategies, detailed photophysical properties, and their applications will help in assisting researchers to overcome existing challenges in designing novel solid state ESIPT fluorophores for promising applications. This review highlights recently developed solid state ESIPT emitters with focus on molecular design strategies and their photophysical properties, reported in the last five years.

Excited-state intramolecular proton-transfer (ESIPT)-inspired solid state emitters

Very bright mechanoluminescence and remarkable mechanochromism using a tetraphenylethene derivative with aggregation-induced emission

Stimuli-responsive microstructures are critical to create adaptable systems in soft robotics and biosciences. For such applications, the materials must be compatible with aqueous environments and enable the manufacturing of three-dimensional structures. Poly(N-isopropylacrylamide) (pNIPAM) is a well-established polymer, exhibiting a substantial response to changes in temperature close to its lower critical solution temperature. To create complex actuation patterns, materials that react differently with respect to a stimulus are required. Here, we introduce functional three-dimensional hetero-microstructures based on pNIPAM. By variation of the local exposure dose in three-dimensional laser lithography, we demonstrate that the material parameters can be altered on demand in a single resist formulation. We explore this concept for sophisticated three-dimensional architectures with large-amplitude and complex responses. The experimental results are consistent with numerical calculations, able to predict the actuation response. Furthermore, a spatially controlled response is achieved by inducing a local temperature increase by two-photon absorption of focused light.

/pdf/controlling-the-shape-of-3d-microstructures-by-temperature-4xqivya32d.pdf

Controlling the shape of 3D microstructures by temperature and light

Solution and solid dual photoluminescence (PL) molecules fill the substantial gap between ACQ and AIE molecules to explore the mechanism of molecular luminescence in greater detail and to facilitate practical applications. A unique arch-bridge-like thiazolo[5,4-b]thieno[3,2-e]pyridine moiety is obtained as a stator after the rigidification of rotor 1 by intramolecular H-bonding of ortho –OH or –NH2 to afford two classes of solid and solution dual PL molecules. As a typical example, DF5 is dual PL active. Moreover, the large Stokes shift with high dual PL efficiency (ΦF up to 51% in the solid state, 80% in DMF, 74% in DMSO, and 100% in water), together with the good thermal stability (Tm > 200 °C and T05 > 200 °C), make it more practical for promising optoelectronic and biological applications.

/pdf/an-arch-bridge-type-fluorophore-for-bridging-the-gap-between-2ouscjmzzy.pdf

An arch-bridge-type fluorophore for bridging the gap between aggregation-caused quenching (ACQ) and aggregation-induced emission (AIE)

Aggregation induced emissive carbazole-based push pull NLOphores: Synthesis, photophysical properties and DFT studies

Pyrazole based solid state emissive NLOphores with TICT characteristics: Synthesis, DFT and TDDFT studies

A new class of red emitting extensively conjugated donor-π-acceptor type dyes bearing coumarin units are investigated for nonlinear optical properties. The photophysical behaviour and the relation between structure and properties of the coumarin "push-pull" derivatives were investigated based on solvatochromism and experimentally observed shifts in emission maxima. The electronic coupling for the electron transfer reaction for the coumarin dyes are calculated with the generalized Mulliken-Hush method. We evaluated non-linear optical (NLO) properties of coumarin dyes using both experimental solvent dependent shift method and computational method. All the investigated coumarin dyes are showing large value for first (β) and second hyperpolarizability (γ). Density functional theory [B3LYP/6-31G(d)] and time dependent density functional theory (TDDFT) computations have been employed to have more understanding of structural, molecular, electronic and photophysical parameters of the coumarin dyes.

Coumarin Push-Pull NLOphores with Red Emission: Solvatochromic and Theoretical Approach.

The electronic structures and photophysical properties of rigid coumarin dyes have been studied by using quantum chemical methods. The ground-state geometries of these dyes were optimized using the Density Functional Theory (DFT) methods. The lowest singlet excited state was optimized using Time -Dependent Density Functional Theory [TD-B3LYP/6-31G(d)]. On the basis of ground- and excited-state geometries, the absorption and emission spectra have been calculated using the DFT and TD-DFT method. All the calculations were carried out in gas phase and in acetonitrile medium. The results show that the absorption maxima and fluorescence emission maxima calculated using the Time-Dependent Density Functional Theory is in good agreement with the available experimental results. To understand the Non- Linear Optical properties of coumarin dyes we computed dipole moment (μ), electronic polarizability (α), mean first hyperpolarizability (βo) and second hyperpolarizability (γ) using B3LYP density functional theory method in conjunction with 6-31G(d) basis set.

Sandip K. Lanke

Papers

Aggregation induced emissive carbazole-based push pull NLOphores: Synthesis, photophysical properties and DFT studies

Pyrazole based solid state emissive NLOphores with TICT characteristics: Synthesis, DFT and TDDFT studies

Coumarin Push-Pull NLOphores with Red Emission: Solvatochromic and Theoretical Approach.

Rigid Coumarins: a Complete DFT, TD-DFT and Non Linear Optical Property Study

Pyrazole based NLOphores: Synthesis, photophysical, DFT, TDDFT studies