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Regiospecific Formation and Unusual Optical Properties of 2,5‐Bis(arylethynyl)rhodacyclopentadienes: A New Class of Luminescent Organometallics 下载免费PDF全文
Dr. Andreas Steffen Dr. Richard M. Ward Dr. Meng Guan Tay Dr. Robert M. Edkins Dr. Fabian Seeler Magda van Leeuwen Dr. Lars‐Olof Pålsson Prof. Dr. Andrew Beeby Dr. Andrei S. Batsanov Prof. Dr. Judith A. K. Howard Prof. Dr. Todd B. Marder 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(13):3652-3666
A series of 2,5‐bis(arylethynyl)rhodacyclopentadienes has been prepared by a rare example of regiospecific reductive coupling of 1,4‐(p‐R‐phenyl)‐1,3‐butadiynes (R?H, Me, OMe, SMe, NMe2, CF3, CO2Me, CN, NO2, ?C?C‐(p‐C6H4?NHex2), ?C?C?(p‐C6H4?CO2Oct)) at [RhX(PMe3)4] ( 1 ) (X=?C?C?SiMe3 ( a ), ?C?C‐(p‐C6H4?NMe2) ( b ), ?C?C?C?C?(p‐C6H4?NPh2) ( c ) or ?C?C?{p‐C6H4‐C?C?(p‐C6H4‐N(C6H13)2)} ( d ) or Me ( e )), giving the 2,5‐bis(arylethynyl) isomer exclusively. The rhodacyclopentadienes bearing a methyl ligand in the equatorial plane (compound 1 e ) have been converted into their chloro analogues by reaction with HCl etherate. The rhodacycles thus obtained are stable to air and moisture in the solid state and the acceptor‐substituted compounds are even stable to air and moisture in solution. The photophysical properties of the rhodacyclopentadienes are highly unusual in that they exhibit, exclusively, fluorescence between 500–800 nm from the S1 state, with quantum yields of Φ=0.01–0.18 and short lifetimes (τ=0.45–8.20 ns). The triplet state formation (ΦISC=0.57 for 2 a ) is exceptionally slow, occurring on the nanosecond timescale. This is unexpected, because the Rh atom should normally facilitate intersystem crossing within femto‐ to picoseconds, leading to phosphorescence from the T1 state. This work therefore highlights that in some transition‐metal complexes, the heavy atom can play a more subtle role in controlling the photophysical behavior than is commonly appreciated. 相似文献
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Subbiah Meenakshisundaram RM. Sockalingam 《Journal of molecular catalysis. A, Chemical》2000,160(2):269-275
Catalytic activity of Os(VIII) in the oxidation of some twenty organic sulfides with sodium salt of N-chlorobenzenesulfonamide (CAB) has been investigated in alkaline (pH8.7) t-butanol–water (1:1 v/v) medium. Significant retarding influence of [OH−] on the reactivity is exhibited. The catalysed reaction is strongly accelerated in the presence of Hg(II). Imperfections are observed in the linear Hammett relationship in the case of –NO2 substituents. 相似文献
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Nano titanium dioxide (nTiO2), generally considered to be toxicologically inert, is manufactured in large quantities and extensively applied in consumer products. The small size and large surface area endow them with an active group or intrinsic toxicity. Advances in instrumentation are making Raman spectroscopy the tool of choice for an increasing number of (bio) chemical applications. One of the great advantages of this technique is its ability to provide information on the concentration, structure and interaction of biochemical molecules in their microenvironments within intact cells and tissues, non-destructively. Zebrafish (Danio rerio), one of the most important vertebrate model organisms used in developmental biology, are increasingly used in biomedical research, particularly as a model of human disease. In the present work, an attempt is made to study the effect of titanium dioxide, both nano and bulk, on the microenvironment of the liver tissues of Zebrafish using FT-Raman spectroscopy. The results of the present study suggest that TiO2 exposure demonstrate a marked influence on the microenvironments of the liver tissues of Zebrafish. A shift to a higher wavenumber and an increase in the intensity of the band at ∼1087 cm−1 in the TiO2 exposed tissues suggest that some of the conformational changes resulting from the alkali recovery process takes place due to TiO2 exposure. The decreased intensity ratio (I3220/I3400) observed in the titanium-exposed tissues suggests a decreased water domain size, which could be interpreted in terms of weaker hydrogen-bonded molecular species of water in the TiO2 exposed tissues. The observed shift of COO− bands to higher frequencies shows the disruption of salt bridges as a result of a change in the oppositely charged partners and due to the enhanced random coil conformation. The variation in the intensity ratio of the tyrosyl doublet (I858/I825) indicates variation in the hydrogen bonding of the phenolic hydroxyl group due to TiO2 exposure. The results further suggest that the microenvironments are greatly altered due to titanium nano exposure when compared to titanium bulk. In conclusion, the results indicate that FT-Raman spectroscopy might be a useful tool for rapid assessment of nano particle biological interactions. 相似文献
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Zhu Wu Jrn Nitsch Julia Schuster Alexandra Friedrich Katharina Edkins Marcel Loebnitz Fabian Dinkelbach Vladimir Stepanenko Frank Würthner Christel M. Marian Lei Ji Todd B. Marder 《Angewandte Chemie (International ed. in English)》2020,59(39):17137-17144
Achieving highly efficient phosphorescence in purely organic luminophors at room temperature remains a major challenge due to slow intersystem crossing (ISC) rates in combination with effective non‐radiative processes in those systems. Most room temperature phosphorescent (RTP) organic materials have O‐ or N‐lone pairs leading to low lying (n, π*) and (π, π*) excited states which accelerate kisc through El‐Sayed's rule. Herein, we report the first persistent RTP with lifetimes up to 0.5 s from simple triarylboranes which have no lone pairs. RTP is only observed in the crystalline state and in highly doped PMMA films which are indicative of aggregation induced emission (AIE). Detailed crystal structure analysis suggested that intermolecular interactions are important for efficient RTP. Furthermore, photophysical studies of the isolated molecules in a frozen glass, in combination with DFT/MRCI calculations, show that (σ, B p)→(π, B p) transitions accelerate the ISC process. This work provides a new approach for the design of RTP materials without (n, π*) transitions. 相似文献
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C McConville RM Kalin D Flood 《Rapid communications in mass spectrometry : RCM》1999,13(13):1339-1345
Current methods for stable oxygen isotopic (delta (18)O) analysis of soil water rely on separation of water from the soil matrix before analysis. These separation procedures are not only time consuming and require relatively large samples of soil, but also have been shown to introduce a large potential source of error. Current research at Queen's University Belfast is focused on using direct equilibration of CO(2) with the pore water to eliminate this extraction step using the automated Multiprep system and a Micromass Prism III isotope ratio mass spectrometer (IRMS). The findings of this research indicate the method is less time consuming, more reliable, and reproducible to within accepted limits (+/-0.1% per thousand delta (18)O). In this study the direct equilibration method is used to analyse delta (18)O tracer profiles in the unsaturated zone of field soils, concurrently with chloride tracer profiles, which can be used to assess infiltration rates and mechanisms through the unsaturated zone. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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RD Harris WS Baker Van Stipdonk MJ RM Crooks EA Schweikert 《Rapid communications in mass spectrometry : RCM》1999,13(14):1374-1380
A suite of keV polyatomic or 'cluster' projectiles was used to bombard unoxidized and oxidized self-assembled monolayer surfaces. Negative secondary ion yields, collected at the limit of single ion impacts, were measured and compared for both molecular and fragment ions. In contrast to targets that are orders of magnitude thicker than the penetration range of the primary ions, secondary ion yields from polyatomic projectile impacts on self-assembled monolayers show little to no enhancement when compared with monatomic projectiles at the same velocity. This unusual trend is most likely due to the structural arrangement and bonding characteristics of the monolayer molecules with the Au(111). Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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V. Vijayasundaram V. Ramasamy PL. RM. Palaniappan 《Journal of Thermal Analysis and Calorimetry》2009,98(1):183-188
The paper presents the changes in the thermal properties of control, arsenic exposed and DMSA treated Labeo rohita bones by using thermo analytical techniques. The result shows that the mass loss due to the thermal decomposition occurs
in three distinct steps due to loss of water, organic and inorganic materials. The arsenic exposed bones present a different
thermal behaviour compared to the control bones. The residue masses are increased due to arsenic exposure, while the DMSA
treatment reduces the residue mass level. These thermal characteristics can be used as a qualitative method to check the metal
accumulation in samples. 相似文献
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Stimulus‐Triggered Formation of an Anion–Cation Exciplex in Copper(I) Complexes as a Mechanism for Mechanochromic Phosphorescence 下载免费PDF全文
Benjamin Hupp Dr. Jörn Nitsch Tanja Schmitt Dr. Rüdiger Bertermann Dr. Katharina Edkins Florian Hirsch Prof. Dr. Ingo Fischer Michael Auth Dr. Andreas Sperlich Priv.‐Doz. Dr. Andreas Steffen 《Angewandte Chemie (International ed. in English)》2018,57(41):13671-13675
The investigation of the mechanisms of mechanochromic luminescence is of fundamental importance for the development of materials for photonic sensors, data storage, and luminescence switches. The structural origin of this phenomenon in phosphorescent molecular systems is rarely known and thus the formulation of structure–property relationships remains challenging. Changes in the M–M interactions have been proposed as the main mechanism with d10 coinage metal compounds. Herein, we describe a new mechanism—a mechanically induced reversible formation of a cation–anion exciplex based on Cu–F interactions—that leads to highly efficient mechanochromic phosphorescence and unusual large emission shifts from UV‐blue to yellow for CuI complexes. The low‐energy luminescence is thermo‐ and vaporesponsive, thus allowing the generation of white light as well as for recovering the original UV‐blue emission. 相似文献
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