Role of Charge Density and Surface Area of Tailored Ionic Porous Organic Polymers for Adsorption and Antibacterial Actions.

The development of high-performance adsorbents for environmental remediation is a current need, and ionic porous organic polymers (iPOPs), due to their high physicochemical stability, high surface area, added electrostatic interaction, and easy reusability, have already established themselves as a better adsorbent. However, research on the structural design of high-performance iPOP-based adsorbents is still nascent. This study explored the building blocks' role in optimizing the polymers' charge density and surface area to develop better polymeric adsorbents.

A Competition among Three Ultrafast Photoinduced Events in Thiotropolone: Internal Conversion vs Intersystem Crossing vs ESIPT.

Gas phase excited-state quantum wavepacket dynamics simulations of the thiotropolone demonstrate the ultrafast triplet formation upon photoexcitation to the dipole-allowed S state. The dominant relaxation pathway of the S-T intersystem crossing, facilitated by the strong spin-orbit coupling and narrow energy gap, competes with the S to S/S internal conversion. The wavepacket populated in T via the former pathway decays to lower triplet states.

Stepwise Excited-State Intramolecular Double Proton Transfer in 1,8-Dihydroxynaphthalene-2,7-dicarbaldehyde.

We theoretically investigate the salient features of stepwise excited-state intramolecular double proton transfer (ESIDPT) in 1,8-dihydroxynaphthalene-2,7-dicarbaldehyde (DHDA). Surface trajectory simulations using the TD-B3LYP/6-31G(d) level of theory reveal that the proton transfer primarily happens via S, wherein about ∼42% of trajectories (40 out of 95) show the single proton transfer alone and another ∼32% (30 out of 95) show double proton transfer. The average time scale for the single proton transfer originating from those ∼42% trajectories is ∼147 fs.

A Siderophore Mimicking Gelation Component for Capturing and Self-Separation of Fe(III) from an Aqueous Solution of Mixture of Metal Ions.

The carbohydrazide-based gelation component N,N,N-(1,3,5-triazine-2,4,6-triyl)tris(benzene-1,3,5-tricarbohydrazide) () was synthesized and characterized using various spectroscopic tools. and trimesic acid () get self-assembled to form metallogel with Fe, specifically through various noncovalent interactions in a DMSO and HO mixture. The self-assembly shows remarkable specificity toward Fe(III) among different transition metal salts.

Stable Inner 2H Tautomer of N-Confused-like Porphyrin Embedded with a Carbazole Subunit: Synthesis, Metal Coordination, and Magnetic and Anion Sensing Studies.

A new class of N-confused porphyrin embedded with a carbazole subunit was prepared via [3 + 1] acid-catalyzed condensation of appropriate precursors. underwent smooth metal complexation with Pd(II) and Cu(II) salts to provide the corresponding diamagnetic and paramagnetic , respectively. The single-crystal X-ray structure of is evident with a square-planar Pd-center through C-H activation of inverted pyrrole.

Significance of Nonadiabatic Effects on Efficient Triplet Generation in Lumazines.

The photophysics of lumazines leading to triplet formation and the effect of thionation are explored in the presence of near-degenerate electronic states. Wave packet simulations are performed on model potential energy surfaces to understand the nonadiabatic population transfer among close-lying excited states. Ultrafast population transfer among singlets opens up new intersystem crossing channels from the higher states.

Exploring a Redox-Active Ionic Porous Organic Polymer in Environmental Remediation and Electrochromic Application.

Here, we report the design and synthesis of a redox-active multifunctional ionic porous organic polymer iPOP-Bpy with exchangeable Br ions, incorporating viologen as a redox-active building block. The material shows not only excellent iodine uptake capacity in the vapor phase (540 wt %) but also in the organic (1009.77 mg g) and aqueous phases (3921.

Synthetic Model for FRET Constructed from Covalently Linked Porphyrin Dimers through a Pyrene Bridge.

We report the synthesis and characterization of two porphyrin arrays CF-PyZnDP and Mes-PyZnDP covalently linked by a pyrene moiety which differs from their substituents at their -positions. The key precursor bis-dipyrromethane linked with a pyrene bridge was prepared by the acid-catalyzed condensation of pyrene-1,6-dialdehyde with excess pyrrole. The synthesis of CF-PyZnDP was carried out via two different synthetic routes, with one being efficient over the other.

Photosensitized Radical-Anion-Driven Metal-Free Selective Reduction of Aldehydes Using Graphene Oxide as an Electron Relay Mediator under Visible Light.

Despite the modern boost, developing a new photocatalytic system for the reduction of aldehydes is still challenging due to their high negative reduction potential. Herein, we have used a metal-free photoinduced electron-transfer system based on a cheap and readily available organic dye eosin Y (EY), graphene oxide (GO), and ammonium oxalate (AO) for photocatalytic reduction of structurally diverse aldehydes under sustainable conditions. The protocol shows remarkable selectivity for the photocatalytic reduction of aldehydes over ketones.

Synthesis, Structure, and Optical Properties of a Bis-Macrocycle Derived from a Highly Emissive 1,3,6,8-Tetra(1-pyrrol-2-yl)pyrene.

A tetra-functionalized pyrene precursor is prepared using the Suzuki-Miyaura coupling of 1,3,6,8-tetrabromopyrene with -Boc-2-pyrroleboronic acid. displayed a blue emission with a high quantum yield (ϕ = 0.89).

Core-Twist Reduces the Triplet Formation Efficiency in Brominated Perylene Diimides.

Bromination is a recent approach to achieve intersystem crossing (ISC) in perylene diimides (PDIs). Herein, we explore the triplet formation dynamics in two tetrabrominated PDI (PDI-Br) positional isomers with planar (P-PDI) and twisted (T-PDI) π-conjugated frameworks. In contrast to the known effect where the planar geometry favors fluorescence, T-PDI shows higher fluorescence (ϕ = 0.

Rapid Intersystem Crossing Induced by Ultrafast Excited-State Intramolecular Proton Transfer in 3-Mercaptopyran-4-one.

Investigation into the photoinduced processes of 3-mercaptopyran-4-one is carried out using trajectory-based surface hopping simulations. Excitation into the near-degenerate higher singlet excited states reveals rapid internal conversion (IC) into S on a sub-50 fs timescale. Excited-state intramolecular proton transfer (ESIPT) also takes place simultaneously with IC.

Regioselective allenylation and propargylation of various -quinone methides using alkynyl azaarenes as pronucleophiles.

We have developed Brønsted base-mediated regioselective allenylation and propargylation of various -quinone methides using unfunctionalized 2-alkynyl azaarenes as pronucleophiles. The appropriate choice of a base provides an opportunity to achieve either an allenylated product or the propargylated product. The use of KOBu as a Brønsted base promotes the formation of allenylated products, whereas NaN(SiMe) furnishes the propargylated products.

Revisiting the Dynamics of Triplet Formation in Anthraquinones.

Triplet formation pathways in 9,10-anthraquinone (AQ) and its hydroxy derivative, 1-hydroxyanthraquinone (HAQ), are studied theoretically. Dynamics simulations on the model singlet-triplet potential energy surfaces within the linear vibronic coupling framework are performed to elucidate possible internal conversion (IC) and intersystem crossing (ISC) pathways in these molecules. An ultrafast IC decay from the "bright" S to S followed by efficient ISC via S-T and S-T pathways fosters a high triplet quantum yield (Φ = 0.

Catechol oxidation promoted by bridging phenoxo moieties in a bis(μ-phenoxo)-bridged dicopper(ii) complex.

A dinuclear copper(ii) complex [Cu(papy)(CHOH)] has been synthesized by reaction of one equiv. of Cu(OAc)·2HO with one equiv. of the tetradentate tripodal ligand Hpapy [-(2-hydroxybenzyl)--(2-picolyl)glycine] and has been characterized by various spectroscopic techniques and its solid state structure has been confirmed by X-ray crystal structure analysis.

Theoretical approach to modeling the early nonadiabatic events of ESIPT originating from three-state conical intersection in quinophthalone.

We explore the excited-state intramolecular proton transfer process of quinophthalone theoretically. This molecule possesses three low-lying singlet excited states ([Formula: see text] and [Formula: see text]) in a narrow energy gap of less than the N-H stretching frequency. Dynamics simulations show nonadiabatic wavepacket transfer to [Formula: see text] and [Formula: see text] upon initiating the wavepacket on [Formula: see text].

Rationalizing the Fluorescence Behavior of Core-Substituted Naphthalene Diimides.

We study the internal conversion (IC) and intersystem crossing (ISC) pathways of low-lying excited electronic states of three core-substituted naphthalene diimides (bNDI, yNDI, and gNDI) using wavepacket simulations within the linear vibronic coupling method. Our wavepacket simulations reproduce the experimental electronic absorption spectra very well. All molecules decay rapidly to S upon populating a higher dipole-allowed singlet excited-state.

Crystal Packing-Driven Selective Hg(II) Ion Sensing Using Thiazolothiazole-Based Water-Stable Zinc Metal-Organic Framework.

A soft acid-soft base interaction is highly predictable. However, we demonstrate how the crystal packing of the newly synthesized zinc framework [Zn(5-AIA)(DPTTZ)]·DMF (where 5-AIA = 5-aminoisophthalic acid, DPTTZ = -di(4-pyridyl)thiazolo-[5,4-]thiazole, DMF = -dimethylformamide) directs an unexpected interaction between the soft acid Hg(II) and the hard base oxygen instead of having a soft center like nitrogen and sulfur in the system attributed to a strong solvent interaction and a favorable ionic radius of Hg(II) ion for oxygen chelation. This engenders selective Hg(II) ion sensing through a "turn-off" emission quenching in water (limit of detection = (2.

Disruption of Antiaromaticity in Structurally Related Expanded Porphyrin-like Macrocycles with Benzene Linkers.

1,4-Phenylene-linked cyclotrimer () and cyclotetramer () have been synthesized via Lewis acid-catalyzed self-condensation of appropriate precursors. Structural and Density Functional Theory (DFT) studies reveal the disruption of annulenic conjugation in both and by linking phenylene rings prevented them from global antiaromaticity. The single crystal X-ray structure of reveals all the nitrogens are pointing toward the macrocyclic core with near-planar and square-shaped geometry, thus in sharp contrast to the ring-strained conformation of .

Ultrafast nonadiabatic excited-state intramolecular proton transfer in 3-hydroxychromone: A surface hopping approach.

We employ the ab initio molecular dynamics within the surface hopping method to explore the excited-state intramolecular proton transfer taking place on the coupled "bright" S (ππ*) and "dark" S (nπ*) states of 3-hydroxychromone. The nonadiabatic population transfer between these states via an accessible conical intersection would open up multiple proton transfer pathways. Our findings reveal the keto tautomer formation via S on a timescale similar to the O-H in-plane vibrational period (<100 fs).

Surface hopping dynamics reveal ultrafast triplet generation promoted by S-T-T spin-vibronic coupling in 2-mercaptobenzothiazole.

We investigate the T formation upon populating the optically "bright" S in 2-mercaptobenzothiazole to interpret the underlying relaxation pathways associated with the experimental decay constants reported by D. Koyama and A. J.

Intersystem crossing pathways in [5]-, [7]-, and [9]cycloparaphenylenes.

We analyze the energetics and internal conversion dynamics of singlet and triplet manifolds to identify the possible intersystem crossing pathways in odd-numbered [n]cycloparaphenylenes ([n]CPPs, n = 5, 7, and 9). Quantum wavepacket propagation calculations within the linear vibronic coupling framework suggest that both [5]- and [7]CPPs rapidly relax to S upon populating "bright" higher singlet excited states. The S-S energy decreases with the increase in CPP size, and hence, [9]CPP exhibits a faster S → S internal conversion decay.

Palladium-Catalyzed Direct C2-Biarylation of Indoles.

Biaryl and indole units are important structural motifs in several bioactive molecules and functional materials. We have accomplished straightforward access to C2-biarylated indole derivatives through palladium-catalyzed C-H activation strategy with a broad range of substrate scope in yields of 24 to 92%. Besides, the UV/visible absorption and fluorescence properties of the ensuing products were explored.

Double intramolecular hydrogen transfer assisted dual emission in a carbazole-embedded porphyrin-like macrocycle.

The introduction of a pyrrole ring at one of the meso positions of carbazole-based porphyrins lowers the structural symmetry and results in dual emission, which strongly depends on the excitation wavelength and temperature. The origin of dual emission induced by NH-tautomerism is confirmed via photophysical and DFT calculations.

Role of Skeletal and O-H Vibrational Motions in the Ultrafast Excited-State Relaxation Dynamics of Alizarin.

The role of two skeletal (C═C and C═O stretch) and O-H vibrational motions in the internal conversion dynamics associated with the coupled S(ππ*, A') -S(nπ*, A″) potential energy surfaces of alizarin are investigated theoretically. Quantum wavepacket dynamics simulations reveal a nonadiabatic population transfer from the "bright" S(ππ*, A') to "dark" S(nπ*, A″) state on a time scale of 10 fs. A detailed analysis of computed structural parameters, energetics, and time-dependent observables suggest that these vibrations promote the nonadiabatic dynamics before initiating the proton transfer process.