Tunable Chiral Second-Order Nonlinear Optical Chromophores Based on Helquat Dications

Fourteen new dipolar cations have been synthesized, containing methoxy or tertiary amino electron donor groups attached to helquat (Hq) acceptors. These Hq derivatives have been characterized as their TfO^– salts by using various techniques including NMR and electronic absorption spectroscopies. UV–vis spectra show intense, relatively low energy absorptions with λ_(max) ≈ 400–600 nm, attributable to intramolecular charge-transfer (ICT) excitations. Single-crystal X-ray structures have been solved for two of the chromophores, one as its PF_6^– salt, revealing centrosymmetric packing arrangements (space groups Pbca and P1̅). Molecular quadratic nonlinear optical (NLO) responses have been determined directly by using hyper-Rayleigh scattering (HRS) with a 800 nm laser, and indirectly via Stark (electroabsorption) spectroscopy for the low energy absorption bands. The obtained static first hyperpolarizabilities β_0 range from moderate to large: (9–140) × 10^(–30) esu from HRS in MeCN and (44–580) × 10^(–30) esu from the Stark data in PrCN. The magnitude of β_0 increases upon either extending the π-conjugation length or replacing a methoxy with a tertiary amino electron donor substituent. Density functional theory (DFT) and time-dependent DFT calculations on selected tertiary amino chromophores confirm that the low energy absorptions have ICT character. Relatively good agreement between the simulated and experimental UV–vis absorption spectra is achieved by using the CAM-B3LYP functional with the 6-311G(d) basis set. The β_(tot) values predicted by using DFT at the same level of theory are large ((472–1443) × 10^(–30) esu in MeCN). Both the theoretical and experimental results show that para-conjugation between Hq and electron donor fragments is optimal, and enlarging the Hq unit is inconsequential with respect to the molecular quadratic NLO response

Helquat Dyes: Helicene-like Push–Pull Systems with Large Second-Order Nonlinear Optical Responses

Helquat dyes combine a cationic hemicyanine with a helicene-like motif to form a new blueprint for chiral systems with large and tunable nonlinear optical (NLO) properties. We report a series of such species with characterization, including determination of static first hyperpolarizabilities β_0 via hyper-Rayleigh scattering and Stark spectroscopy. The measured β_0 values are similar to or substantially larger than that of the commercial chromophore E-4′-(dimethylamino)-N-methyl-4-stilbazolium. Density functional theory (DFT) and time-dependent DFT calculations on two of the new cations are used to probe their molecular electronic structures and optical properties. Related molecules are expected to show bulk second-order NLO effects in even nonpolar media, overcoming a key challenge in developing useful materials

Strategic analysis of the company Mokate Czech s.r.o.

The aim of the bachelor thesis is to evaluate the current position of Mokate Czech s.r.o. on the tea market using individual methods of strategic analysis and provide the company with recommendations for further development in the future. The thesis is divided into a theoretical and a practical part. At the beginning of the theoretical part, the company's strategy will be defined, hence the mission, vision, and strategic goals. Concepts used to analyze the external environment include PESTLE analysis, industry and competition analysis, and Porter's five forces model. Sub-analyses dedicated to the internal environment of the company are VRIO analysis, financial analysis, and portfolio analysis. The synthesis includes a SWOT analysis, in which the findings from previous analyzes will be linked. In the practical part, the concepts will be applied to a selected company.Cílem bakalářské práce je zhodnocení současného postavení společnosti Mokate Czech s.r.o. na trhu s čajem pomocí jednotlivých metod strategické analýzy a poskytnout podniku doporučení pro další rozvoj do budoucna. Práce je rozčleněna na teoretickou a praktickou část. V úvodu teoretické části dojde k vymezení strategie firmy, tudíž mise, vize a strategických cílů. Mezi koncepty využité pro analýzu vnějšího okolí patří PESTLE analýza, analýza odvětví a konkurence, a Porterův model pěti sil. Dílčími analýzami věnujícími se vnitřnímu prostředí společnosti jsou VRIO analýza, finanční analýza a portfolio analýza. Syntéza zahrnuje SWOT analýzu, ve které budou poznatky s předchozích analýz propojeny. V části praktické budou koncepty aplikovány na vybranou společnost

Chiroptical Redox Switching of Tetra‐Cationic Derivatives of Azoniahelicenes

New tetra- and di-cationic azoniahelicenes provide electrochemical, spectroelectrochemical and electronic circular dichroism (ECD) data reflecting their differences in electron transfer (ET) kinetics. Di-cationic helquats containing two seven-membered rings are irreversibly reduced in two ET steps. Substitution by redox-active ethenylpyridinium in the α or γ position with respect to nitrogen atoms of the helquat core yields tetra-cationic derivatives with reversible ET steps and communicating redox centres. Redox-inactive substituents in di-cationic azoniahelicenes retain ET irreversibility. Redox switching of ECD of tetra-cationic enantiomers was observed. Unlike fully aromatic helquat, the ECD response of tetra-cationic helquats to periodic reduction-oxidation cycles is slower, owing to a strong adsorption on electrodes. Quantum chemical calculations (DFT) indicate that the first ET step of tetra-cationic derivative substituted in the γ position yields a folded structure, which favours the internal donor-acceptor interaction. This explains the spectroelectrochemical differences between both tetra-cations

Bio- and Air-Tolerant Carbon–Carbon Bond Formations 1023 BIO- AND AIR-TOLERANT CARBON–CARBON BOND FORMATIONS VIA ORGANOMETALLIC RUTHENIUM CATALYSIS

Dedicated to Dr. Alfred Bader on the occasion of his 85th birthday in recognition of his outstanding contributions as a chemist, enterpreneur, and benefactor. Selected [2+2+2] cycloadditions, alkene–alkyne coupling and fusion of enyne with diazo compound, all triggered by an artificial organometallic ruthenium catalyst are demonstrated to proceed under ambient aerobic aqueous conditions in presence of bodily fluids or cell lysate. To the best of our knowledge, these are the first examples of bio- and air-tolerant C–C bond formation catalyzed by an artificial organometallic compound