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A novel, versatile and modular route to unsymmetrical diborane(4) derivatives bearing either two different diol moieties or one diol and one diamine moiety is presented. Utilising the very basic approach of reacting a boron nucleophile with a boron electrophile to establish the B–B bond allows a simple variation of the two individual boron moieties. The copper(i) boryl complexes used as nucleophilic boron sources are readily accessible from commercially available symmetrical diborane(4) derivatives, whilst equally readily available boron halide derivatives are used as electrophiles. Seven previously inaccessible diborane(4) derivatives were obtained and fully characterised, including single crystal X-ray structure determinations, illustrating the broad scope of the method. [ABSTRACT FROM AUTHOR]

The unsymmetrical diborane(4) pinB–B((RN)2(C6H4)) (R = Me, Bn) reacts with [(Me3P)4Rh–X] (X = Me, OtBu) giving predominantly either [(Me3P)4Rh–Bpin] or [(Me3P)3Rh–B((RN)2(C6H4))] depending on X. At low temperatures in the presence of excess PMe3 the unprecedented equatorial boryl complex [(Me3P)4Rh–B((MeN)2(C6H4))] is formed. [ABSTRACT FROM AUTHOR]

Chronic venous insufficiency of the lower limbs is a disease which is caused by an increased blood pressure inside the veins of the leg and the resulting increase of the contained blood volume. This work focuses on developing a device which uses impedance plethysmography, also known as impedance phlebography, to obtain information about the blood volume in the lower leg and provides the possibility to measure the impedance semi contact-less, e.g. through compression stockings. Furthermore a real-time beat-to-beat interval detection algorithm was implemented. Finally, the function of the developed impedance measuring system and the whole system was verified by comparing it with a gold standard. In comparison to the conductive coupling, the system performed similarly. The analysis showed that the developed system is suitable for semi-capacitive IPG. The algorithm was implemented conservatively since it provided a good false-positive rate of 0 %, but only a moderate sensitivity of about 68 %. Reliable and continuous measurement of the pulse signal was only possible in periods of immobility.

The copper catalyzed hydroboration of alkynes with B 2 pin 2 was studied by in detail studies of individual relevant steps along the catalytic pathway. A number of reaction steps were retraced by in situ NMR spectroscopy as well as central intermediates and side-products were isolated and comprehensively characterized. A copper boryl complex is central to the catalytic process by inserting the terminal alkyne substrate into the B-Cu bond. The selectivity of this step - depending on the NHC auxiliary ligand - determines the α/β selectivity observed in the product. The latter complex is protonated by the auxiliary alcohol reagent resulting in hydroboration product formation and formation of a Cu alkoxido complex. Reaction of the latter with B 2 pin 2 results in the regeneration of the central copper boryl complex. This alcoholysis step depends on the acidity of the alcohol, in particular on the relative acidity of the alcohol vs. the alkyne substrate. A number of side reactions leading to the hydrogenation product of the alkyne substrate and a bis hydroborated product were identified and studied in some detail. It is concluded that the performance of a particular catalytic system depends crucially on the relative acidities of the reagents and generalizations may be difficult., (© 2024 The Authors. Chemistry - An Asian Journal published by Wiley-VCH GmbH.)

The resolution of 3D electron diffraction (ED) data of small-molecule crystals is often relatively poor, due to either electron-beam radiation damage during data collection or poor crystallinity of the material. Direct methods, used as standard for crystal structure determination, are not applicable when the data resolution falls below the commonly accepted limit of 1.2 Å. Therefore an evaluation was carried out of the performance of molecular replacement (MR) procedures, regularly used for protein structure determination, for structure analysis of small-molecule crystal structures from 3D ED data. In the course of this study, two crystal structures of Bi-3812, a highly potent inhibitor of the oncogenic transcription factor BCL6, were determined: the structure of α-Bi-3812 was determined from single-crystal X-ray data, the structure of β-Bi-3812 from 3D ED data, using direct methods in both cases. These data were subsequently used for MR with different data types, varying the data resolution limit (1, 1.5 and 2 Å) and by using search models consisting of connected or disconnected fragments of BI-3812. MR was successful with 3D ED data at 2 Å resolution using a search model that represented 74% of the complete molecule., (open access.)

The unsymmetrical diborane(4) derivative [(d(CH 2 P( i Pr) 2 )abB)-Bpin] ( 1 ) proved to be a versatile PBP boryl pincer ligand precursor for Co(I) ( 2a , 4a ), Rh(I) ( 2 - 3b ) and Ir(I/III) ( 2 - 3c , 5 - 6c ) complexes, in particular of the types [(d(CH 2 P( i Pr) 2 )abB)M(PMe 3 ) 2 ] ( 2a - c ) and [(d(CH 2 P( i Pr) 2 )abB)M-PMe 3 ] ( 2b - c ). Whilst similar complexes have been obtained before, for the first time, the coordination chemistry of a homologous series of PBP pincer complexes, in particular the interconversion of the five- and four-coordinate complexes 2a - c / 3a - c , was studied in detail. For Co, instead of the mono phosphine complex 2a , the dinitrogen complex [(d(CH 2 P( i Pr) 2 )abB)Co(N 2 )(PMe 3 )] ( 4a ) is formed spontaneously upon PMe 3 abstraction from 2a in the presence of N 2 . All complexes were comprehensively characterised spectroscopically in solution via multinuclear (VT-)NMR spectroscopy and structurally in the solid state through single-crystal X-ray diffraction. The unique properties of the PBP ligand with respect to its coordination chemical properties are addressed.

Driven by the great potential of solar energy conversion this study comprises the evaluation and comparison of two different design approaches for the improvement of copper based photosensitizers. In particular, the distinction between the effects of a covalently linked and a directly fused naphthalimide unit was assessed. For this purpose, the two heteroleptic Cu(I) complexes CuNIphen ( NIphen = 5-(1,8-naphthalimide)-1,10-phenanthroline) and Cubiipo ( biipo = 16H-benzo-[4',5']-isoquinolino-[2',1',:1,2]-imidazo-[4,5-f]-[1,10]-phenanthroline-16-one) were prepared and compared with the novel unsubstituted reference compound Cuphen ( phen = 1,10-phenanthroline). Beside a comprehensive structural characterization, including two-dimensional nuclear magnetic resonance spectroscopy and X-ray analysis, a combination of electrochemistry, steady-state and time-resolved spectroscopy was used to determine the electrochemical and photophysical properties in detail. The nature of the excited states was further examined by (time-dependent) density functional theory (TD-DFT) calculations. It was found that CuNIphen exhibits a greatly enhanced absorption in the visible and a strong dependency of the excited state lifetimes on the chosen solvent. For example, the lifetime of CuNIphen extends from 0.37 µs in CH 2 Cl 2 to 19.24 µs in MeCN, while it decreases from 128.39 to 2.6 µs in Cubiipo . Furthermore, CuNIphen has an exceptional photostability, allowing for an efficient and repetitive production of singlet oxygen with quantum yields of about 32%., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Yang, Doettinger, Kleeberg, Frey, Karnahl and Tschierlei.)

The oxidative addition of five diborane(4) derivatives, symmetrical and unsymmetrical, to [Rh(PMe 3 ) 3 Cl] was studied. Only for the more electron poor diboron derivatives, B 2 cat 2 , B 2 pin 2 and catB-Bpin the resulting octahedral bis-boryl complexes [(PMe 3 ) 3 Rh(boryl) 2 Cl] were obtained, while for the more electron rich congeners only the equilibrium oxidative addition (catB-Bdmab) or no significant reaction (pinB-Bdmab) was observed (pin = (OCMe 2 ) 2 , cat = 1,2-O 2 C 6 H 4 , dmab = 1,2-(NMe) 2 C 6 H 4 ). By abstraction of the chlorido ligand with NaBArF (BArF = tetrakis-[3,5-bis-(trifluormethyl)-phenyl]-borat) in the presence of a neutral ligand (L = PMe 3 , MeCN, MeNC) the corresponding cationic octahedral complexes [(PMe 3 ) 3 Rh(boryl) 2 L] + were obtained. All isolated complexes were fully characterised including single crystal X-ray diffraction and heteronuclear, temperature dependent NMR spectroscopy. Whilst the complexes [(PMe 3 ) 3 Rh(boryl) 2 Cl] and [(PMe 3 ) 3 Rh(boryl) 2 L] + show many similarities, their detailed structural and spectroscopic properties depend crucially on the properties of both boryl ligands.

The N-H deprotonation of the diaminodialkoxido diborane(4) pinB-Bdab (1) (pin: (OCMe 2 ) 2 , dab: 1,2-(NH) 2 C 6 H 4 ), is crucial for the electrophilic N -functionalisation towards unsymmetrical diborane(4) reagents. An N-H deprotonated diborane(4) comprises Lewis basic nitrogen atoms and at the same time Lewis acidic boron atoms. This bifunctionality governs its reactivity and structural chemistry. Whilst bases such as Na(hmds), t BuLi or Li(tmp) readily effect a single deprotonation of 1, the second deprotonation is less straightforward and cleanly only achieved with Li(tmp) as a strong but little nucleophilic base. The N-H deprotonated diborane(4) derivatives readily dimerise to give B(sp 2 ) 2 B(sp 3 ) 2 N 2 six-membered ring Lewis base adducts. The structural chemistry of this class of compounds was studied in detail in the solid state by single crystal X-ray diffraction as well as in solution by NMR spectroscopy.

The substance class of the well-known Cinchona alkaloids is widened by 6'-Amino-cinchonine and 6'-Amino-cinchonidine, novel compounds which incorporate a primary amino function in the quinolinic ring system. These key intermediates open the field for a range of fruitful chemistry. Here is described a short and direct pathway for the synthesis of triazole containing derivatives of the above-mentioned substances using the [3 + 2] Huisgen cycloaddition. For this purpose, the amines were first converted into the corresponding azides. Based on this, non-substituted and silyl-protected triazoles were synthesized as examples. Furthermore, didehydrated derivatives of quincorine and quincoridine were used as addition partners, resulting in compounds that carry the quinuclidine ring of the cinchona alkaloids at both ends. Some of these compounds were examined radiographically to investigate the position of the quinuclidine ring to the triazole. The solid-state structures of compounds 10 , 11 and 28 were determined by X-ray diffraction analyses.

The B-B bond activation of the diborane(4) derivatives B 2 cat 2 with the copper(I) alkoxido complex [(SIDipp)Cu-O tBu] delivers, depending on the solvent, either the linear boryl complex [(SIDipp)Cu-Bcat] from PhMe or the μ-boryl complex [((SIDipp)Cu) 2 Bcat][cat 2 B] from THF. The relevant conversion of the linear boryl complex to the μ-boryl complex occurs in the polar solvent via formal boryl anion abstraction by the Lewis acid catB-O tBu, concomitantly formed during the B-B activation. With Lewis acids such as BPh 3 or [CPh 3 ][BArF] (reversible), boryl abstraction from the linear complexes [(SIDipp)Cu-Bcat] or [(SIDipp)Cu-Bdmab] occurs and results in the μ-boryl complexes [((SIDipp)Cu) 2 Bcat/dmab][Ph 3 B-Bcat/dmab] and [((SIDipp)Cu) 2 Bcat][BArF]. The formation of [((SIDipp)Cu) 2 Bcat][cat 2 B] is generally accompanied by the concomitant formation of the μ-hydrido complex [((SIDipp)Cu) 2 H][cat 2 B]. The spiroborate [cat 2 B] - is formed from the initially formed Lewis acid/base adduct [catB-B(O tBu)cat] - presumably in a process that involves the glass surface of the reaction vessel. All complexes are thoroughly characterized structurally as well as spectroscopically, in particular with respect to the dynamic behavior of the μ-boryl complexes in solution.

A series of five unsymmetrical platinum(ii) bis-boryl complexes, bearing two distinct boryl ligands, are obtained by the oxidative addition reaction of unsymmetrical diborane(4) derivatives, bearing either two different dialkoxy or one dialkoxy and one diamino boryl moiety, with [(Ph 3 P) 2 Pt(C 2 H 4 )]. All five complexes were structurally and spectroscopically characterised. The bis-boryl platinum(ii) complexes exhibit slightly distorted square-planar cis -boryl structures with acute B-Pt-B angles, short B⋯B distances of 2.44-2.55 Å and relatively long trans -boryl P-Pt distances around 2.34 Å. The 31 P- 195 Pt NMR coupling constants are indicative for the strongly donating/ trans -influencing boryl ligands. Despite the structural and spectroscopic data at hand no finally conclusive order of the donor properties/ trans -influence of the boryl ligands can be deduced on the basis of these data. This may be explained by an (residual) interaction of two boryl ligands., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A novel, versatile and modular route to unsymmetrical diborane(4) derivatives bearing either two different diol moieties or one diol and one diamine moiety is presented. Utilising the very basic approach of reacting a boron nucleophile with a boron electrophile to establish the B-B bond allows a simple variation of the two individual boron moieties. The copper(i) boryl complexes used as nucleophilic boron sources are readily accessible from commercially available symmetrical diborane(4) derivatives, whilst equally readily available boron halide derivatives are used as electrophiles. Seven previously inaccessible diborane(4) derivatives were obtained and fully characterised, including single crystal X-ray structure determinations, illustrating the broad scope of the method.

Heteroleptic N-heterocyclic dicarbene-diphosphorus species were prepared by reaction of the carbene-phosphinidene adduct (IPr)PSiMe 3 (1, IPr = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) with the carbene-phosphorus trichloride adduct (IMes)PCl 3 (2, IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene), which furnished the dichloride [(IPr)PPCl(IMes)]Cl (3). Reduction of 3 with potassium graphite (KC 8 ) afforded [(IPr)PP(IMes)] (4). The corresponding radical cation [(IPr)PP(IMes)]˙ + (5˙ + ) is isolated as [5]PF 6 by reaction of 4 with ferrocenium hexafluorophosphate, whereas complexes containing the corresponding dication [(IPr)PP(IMes)] 2+ (6 2+ ) can be isolated as the gallate and borate salts [6](GaCl 4 ) 2 and [6](BAr F ) 2 by chloride abstraction from 3 with GaCl 3 or sodium tetrakis[bis(3,5-trifluoromethyl)phenyl]borate (NaBAr F ), respectively. The asymmetric set of N-heterocyclic carbene ligands allows to establish 1 J PP coupling constants of 249 Hz for 4 and 543 Hz for [6](GaCl 4 ) 2 . Based on X-ray diffraction analyses, the molecular structures of 4, 5˙ + and 6 2+ reveal a consecutive shortening of the P-P bond lengths, in agreement with the presence of a phosphorus-phosphorus single bond in 4 and a double bond in 6 2+ , which is best described as a dicationic diphosphene according to density functional theory (DFT) calculations.

Cu I -catalyzed silylation reactions involving silylboranes (in particular, pinB-SiMe 2 Ph (1)) as silyl sources have recently gained considerable attention. One of the most efficient and versatile and yet simplest catalyst systems consists of CuCN/NaOMe; however, nothing is known about the catalytically relevant species. Using an NHC-based model catalyst, copper silyl complexes of the type [(NHC)Cu-SiMe 2 Ph] have been established to be crucial species in these catalytic processes. The well-defined and spectroscopically and structurally characterized complex [(18-C-6)K][NC-Cu-OtBu] (2), as a model for the catalytic system, CuCN/NaOMe, shows comparable catalytic activity toward established, exemplary substrates (aldehydes, imines, α,β-unsaturated carbonyls) and in extension allows the efficient silylation of ketones. In addition, a number of peculiarities of the catalytic reaction are readily rationalized on the basis of the mechanistic insight already established using [(NHC)Cu-SiMe 2 Ph] as a model catalyst. Analogously to the NHC model system, the reaction of 2 with the silylborane 1 furnishes the silylcyanocuprate [(18-C-6)K][NC-Cu-SiMe 2 Ph] (3) as a potential crucial intermediate in these silylation reactions also suggesting mechanistic similarities between (NHC)Cu- and CuCN/NaOMe-based catalyst systems. Moreover, 3 and [(NHC)Cu-SiMe 2 Ph] complexes also share structurally distinctive features. In the solid state 3 either exists as a linear, two-coordinated copper complex or, depending on the conditions of crystallization, forms binuclear μ-silyl bridged dimers exhibiting very short Cu···Cu distances. Both structural motifs are also known for [(NHC)Cu-SiR 3 ] complexes. These findings give an initial insight into the versatile structural chemistry of certain silylcyanocuprates; in particular, the finding of dinuclear silylcuprates gives rise to the question whether these dimeric species are of mechanistic relevance for the catalytic processes. However, all peculiarities of the investigated catalytic reaction can readily be rationalized on the basis of the mechanistic details established using (NHC)Cu model complexes.

In this detailed study we report on the structures of the widely employed diboron(4) compounds bis(pinacolato)diboron (B 2 pin 2 ) and bis(neopentyl glycolato)diboron (B 2 neop 2 ), as well as bis(ethylene glycolato)diboron (B 2 eg 2 ) and tetrakis(dimethylamino)diboron (B 2 (NMe 2 ) 4 ), and their reactivity, along with that of bis(catecholato)diboron (B 2 cat 2 ) with backbone saturated and backbone unsaturared N-heterocyclic carbenes (NHCs) of different steric demand. Depending on the nature of the diboron(4) compound and the NHC used, Lewis-acid/Lewis-base adducts or NHC ring-expansion products stemming from B-B and C-N bond activation have been observed. The corresponding NHC adducts and NHC ring-expanded products were isolated and characterised via solid-state and solution NMR spectroscopy and X-ray diffraction. In general, we observed B-B bond and C-N bond activation at low temperature for B 2 eg 2 , at room temperature for B 2 neop 2 and at higher temperature for B 2 cat 2 . The reactivity strongly depends on steric effects of the NHCs and the diboron(4) compounds, as well as on the corresponding Lewis-basicity and Lewis-acidity. Our results provide profound insight into the chemistry of these diboron(4) reagents with the nowadays ubiquitous NHCs, the stability of the corresponding NHC adducts and on B-B bond activation using Lewis-bases in general. We demonstrate that B-B bond activation may be triggered even at temperatures as low as -40 °C to -30 °C without any metal species involved. For example, the reactions of B 2 eg 2 with sterically less demanding NHCs such as Me 2 Im Me and iPr 2 Im in solution led to the corresponding ring-expanded products at low temperatures. Furthermore, boronium [L 2 B(OR) 2 ] + and borenium [LB(OR) 2 ] + cations have been observed from the reaction of the bis-borate B 2 eg 3 with the NHCs iPr 2 Im and Me 2 Im Me , which led to the conclusion that the activation of bis-borates with NHCs (or Lewis-bases in general) might be a facile and simple route to access such species.

The reaction of the 2-(trimethylsilyl)imidazolium triflate 9 with diarylboron halides (4-R-C 6 H 4 ) 2 BX (R=H, X=Br; R=CH 3 , X=Cl; R=CF 3 , X=Cl) afforded the NHC-stabilized borenium cations 10 a-c. Cyclic voltammetry revealed a linear correlation between the Hammett parameter σ p of the para substituent and the half-wave potential. Chemical reduction with decamethylcobaltocene, [(C 5 Me 5 ) 2 Co], furnished the corresponding radicals 11 a-c; their characterization by EPR spectroscopy confirmed the paramagnetic character of 11 a-c, with large hyperfine coupling constants to the boron isotopes 11 B and 10 B, while delocalization of the unpaired electron into the NHC is negligible. DFT calculations of the percentage of spin density distribution between the carbene (NHC) and the boryl fragments (BR 2 ) revealed for 11 a-c a spin density ratio (BR 2 /NHC) of ca. 9:1, which underlines their distinct boryl radical character. The molecular structure of the most stable species 11 c was established by X-ray diffraction analysis., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A series of complexes of the type [(NHC)Cu-ER3] (NHC = IDipp, IMes, ItBu, Me2IMe, and ER3 = SiMe2Ph, SiPh3, SnMe3) and [(NHC)Cu-R'] (NHC = IDipp, Me2IMe and R' = Ph, C≡CPh) was synthesized in good yields by the reaction of the corresponding [(NHC)Cu-OtBu] complex with the respective silylborane pinB-ER3 (pin = OCMe2CMe2O; ER3 = SiMe2Ph, SiPh3), the stannylborane ((C2H4)(iPrN)2)B-SnMe3, or a boronic acid ester pinB-R' (R' = Ph, C≡CPh). Solid structures of all complexes were systematically studied by X-ray diffraction analysis. The solid state structures of the complexes [(NHC)Cu-ER3] show a dependence of the structural motif from the steric properties of the NHC ligand. The sterically demanding NHC ligands (IDipp, IMes, ItBu) lead to monomeric, linear complexes [(NHC)Cu-ER3], while with the less demanding Me2IMe ligand, polynuclear, μ-ER3-bridged complexes with ultrashort Cu···Cu distances are observed. For the related complexes [(NHC)Cu-R'] no analogous complexes with bridging anionic ligands are realized. Instead, irrespective of the NHC ligand, linear coordinated copper complexes of different types are formed. (29)Si heteronuclear solution NMR spectroscopic data on [(NHC)Cu(I)-SiR3] exhibit distinctly different chemical shifts for the (in the solid state) monomeric and dimeric complexes suggesting different structure types also in solution. This agrees well with the observation of a trinuclear complex [(Me2IMe)Cu-SnMe3]3 both in the solid state and in solution. Initial catalytic studies suggest that [(NHC)Cu-OtBu] complexes (NHC = ItBu, Me2IMe) are, in addition to the established [(IDipp)Cu-OtBu] complex, efficient precatalysts for the silylation of aldehydes and α,β-unsaturated ketones with pinB-SiMe2Ph.

Chronic venous insufficiency of the lower limbs is often underestimated and, in the absence of therapy, results in increasingly severe complications, including therapy-resistant tissue defects. Therefore, early diagnosis and adequate therapy is of particular importance. External counter pulsation (ECP) therapy is a method used to assist the venous system. The main principle of ECP is to squeeze the inner leg vessels by muscle contractions, which are evoked by functional electrical stimulation. A new adaptive trigger method is proposed, which improves and supplements the current therapeutic options by means of pulse synchronous electro-stimulation of the muscle pump. For this purpose, blood flow is determined by multi-sensor plethysmography. The hardware design and signal processing of this novel multi-sensor plethysmography device are introduced. The merged signal is used to determine the phase of the cardiac cycle, to ensure stimulation of the muscle pump during the filling phase of the heart. The pulse detection of the system is validated against a gold standard and provides a sensitivity of 98% and a false-negative rate of 2% after physical exertion. Furthermore, flow enhancement of the system has been validated by duplex ultrasonography. The results show a highly increased blood flow in the popliteal vein at the knee.

Lewis base adducts of tetra-alkoxy diboron compounds, in particular bis(pinacolato)diboron (B2 pin2 ), have been proposed as the active source of nucleophilic boryl species in metal-free borylation reactions. We report the isolation and detailed structural characterization (by solid-state and solution NMR spectroscopy and X-ray crystallography) of a series of anionic adducts of B2 pin2 with hard Lewis bases, such as alkoxides and fluoride. The study was extended to alternative Lewis bases, such as acetate, and other diboron reagents. The B(sp(2) )-B(sp(3) ) adducts exhibit two distinct boron environments in the solid-state and solution NMR spectra, except for [(4-tBuC6 H4 O)B2 pin2 ](-) , which shows rapid site exchange in solution. DFT calculations were performed to analyze the stability of the adducts with respect to dissociation. Stoichiometric reaction of the isolated adducts with two representative series of organic electrophiles-namely, aryl halides and diazonium salts-demonstrate the relative reactivities of the anionic diboron compounds as nucleophilic boryl anion sources., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We have synthesized a series of luminescent trigonal [CuX(dtbphen)] (X = I (), Br (), Cl (), CN (), dtbphen = 2,9-di-tert-butylphenanthroline) and tetrahedral [Cu2(μ-I)2(L)2] (L = phenanthroline (), 2,9-dimethylphenanthroline ()) copper diimine complexes. Bearing in mind the chemical simplicity of this class of long-known Cu(i) phenanthroline compounds, it is surprising that they exhibit non-trivial photophysical properties, which have not been fully recognized. They display broad XMLCT absorption between ca. 450-600 nm, and the broad emission between ca. 550-850 nm in the solid state occurring with lifetimes on the μs timescale indicates phosphorescence, although the energetic overlap between excitation and emission suggests thermally activated delayed fluorescence (TADF) from S1. In line with the latter assumption, low temperature measurements of in the solid state show an energetic separation of emission and excitation. However, a counter-intuitive decrease of emission intensity and simultaneous increase of the emission lifetime at low temperatures are observed for , which indicates two triplet states also being involved. Our DFT and TD-DFT calculations show that emission from the lowest excited triplet state T1 is of (3)LMXCT nature, separated by only ca. 0.16 eV from S1. Low temperature photophysical measurements at 77 K in a glassy matrix of in 2-Me-THF and of in the solid state are in agreement with the theoretical results, revealing in addition that π-interactions in the solid state also greatly influence the photophysical properties, making a clear conclusion towards TADF ambiguous. This study suggests that other related simple and long-known Cu(i) systems may exhibit a similar, more complex excited state behavior than previously appreciated, involving several emitting states and important intermolecular interactions.

A series of trimethylstannyl potassium complexes [K(L)SnMe3] with different auxiliary ligands L (L = 18-C-6, (TMEDA)2 (TMEDA = tetramethylethylenediamine), and (12-C-4)2) were synthesized by alkoxide-induced B-Sn bond cleavage. X-ray structure determinations were performed for all these complexes, and the structural chemistry was studied in detail. For L = 18-C-6 and (TMEDA)2 the solid state structures comprise polymeric [K(L)SnMe3]n chains containing bidentate trimethylstannyl anions bridging two [K(L)](+) ions, featuring unsymmetrical coordination of the [K(L)](+) ion by K-Sn and K-H3C interactions as a central structural motif. In contrast, for L = (12-C-4)2, separated [K(12-C-4)2](+) and [SnMe3](-) ions are observed. Unexpectedly, in the presence of tetrahydrofuran (THF), [K(18-C-6)SnMe3]n forms upon crystallization a new species consisting of separated [K(18-C-6)(THF)2](+) and [(Me2SnCH3)K(18-C-6)SnMe3](-) ions. In this unsymmetrical anion two trimethylstannyl anions coordinate a single [K(18-C-6)](+) ion; one trimethylstannyl anion coordinates via a K-Sn interaction, and the second coordinates via a K-H3C interaction. Simulations of the mechanochemical properties (compliance constants) applying approximated density functional theory revealed that both interactions are very soft and are of comparable strength. Moreover, according to our gas phase simulations the unsymmetrically coordinated [(Me2SnCH3)K(18-C-6)SnMe3](-) is indeed thermodynamically favored over both possible symmetrical isomers with either K-Sn or K-H3C coordination. Furthermore, the existence of multiple species due to the two coordination modes and aggregates of [K(18-C-6)SnMe3] in solution is suggested by NMR spectroscopic studies using (1)H, NOESY/ROESY, and (1)H pulsed field gradient diffusion experiments.

A first systematic study upon the preparation and exploration of a series of iron 10-thiacorroles with simple halogenido (F, Cl, Br, I), pseudo-halogenido (N3 , I3 ) and solvent-derived axial ligands (DMSO, pyridine) is reported. The compounds were prepared from the free-base octaethyl-10-thiacorrole by iron insertion and subsequent ligand-exchange reactions. The small N4 cavity of the ring-contracted porphyrinoid results in an intermediate spin (i.s., S=3/2) state as the ground state for the iron(III) ion. In most of the investigated cases, the i.s. state is found unperturbed and independent of temperature, as determined by a combination of X-ray crystallography and magnetometry with (1) H NMR-, EPR-, and Mössbauer spectroscopy. Two exceptions were found. The fluorido iron(III) complex is inhomogenous in the solid and contains a thermal i.s. (S=3/2)→high spin (h.s., S=5/2) crossover fraction. On the other side, the cationic bis(pyridine) complex resides in the expected low spin (l.s., S=1/2) state. Chemically, the iron 10-thiacorroles differ from the iron porphyrins mainly by weaker axial ligand binding and by a cathodic shift of the redox potentials. These features make the 10-thiacorroles interesting ligands for future research on biomimetic catalysts and model systems for unusual heme protein active sites., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A series of homologous potassium triphenylelement complexes [K(18-crown-6)EPh3] 6a-e of group 14 elements (E = C, Si, Ge, Sn, Pb) was synthesised by alkoxide induced heterolytic cleavage of boron-element compounds. The complexes 6a-e are isolated as storable solids possibly useful as sources of nucleophilic [EPh3](-) moieties. The solid state structures of 6a-e were established by X-ray crystal structure determination. Whilst all structures can be described as polymeric chains consisting of alternating [K(18-crown-6)](+) and [EPh3](-) units, the interaction within each chain varies systematically with the coordination properties of E. For Si and Ge, classical E-K coordination along with secondary phenyl-K interactions are characteristic, whilst for Sn and Pb, potassium coordination via the phenyl π-system is observed due to inefficient coordination by the free electron pair localised in an 'inert' s-orbital. The carbon derivative is exceptional as the central sp(2)-hybridised carbon atom gives rise to extensive charge delocalisation and coordination via these partially charged π-systems. A (1)H-(1)H NOESY NMR spectroscopic study in THF-d8 suggests appreciable anion/cation interactions for Si to Pb and hence the presence of contact ion pairs.

Mixing CuCl2⋅2 H2O with benzylamine in alcoholic solutions led to an extremely colorful chemistry caused by the formation of a large number of different complexes. Many of these different species could be structurally characterized. These include relatively simple compounds such as [Cu(L(1))4Cl2] (L(1) = benzylamine) and (HL(1))2[CuCl4]. Most interestingly is the easy formation of two cluster complexes, one based on two cluster units Cu4OCl6(L(1))4 connected through one [Cu(L(1))2Cl2] complex and one based on a cubane-type cluster ([Cu4O4](C11H14)4Cl4). Both clusters proved to be highly reactive in a series of oxidation reactions of organic substrates by using air or peroxides as oxidants. Furthermore, it was possible to isolate and structurally characterize ([Cu(L(1))Cl]3 and [Cu(benz2mpa)2]CuCl2 (benz2mpa = benzyl-(2-benzylimino-1-methyl-propylidene)-amine), two copper(I) complexes that formed in solution, demonstrating the high redox activity of the cluster systems. In addition, it was possible to solve the molecular structures of the compounds Cu4OCl6(MeOH)4, [Cu(MeOH)2Cl2], [Cu(aniline)2Cl2], and an organic side product (HC13 H19 NOCl). In fact all determined structures are of a known type but the chemical relation between these compounds could be explained for the first time. The paper describes these different compounds and their chemical equilibria. Some of these complexes seem to be relevant in catalytic oxidation reactions and their reactivity is discussed in more detail., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The first direct borylation of a C-H bond at the 4-position of pyrene was achieved using [Ir(COD)Cl](2)/dtbpy as the catalyst precursor and B(2)pin(2) as the boron source. The position-related photophysical properties of pyrene derivatives are reported.

The Lewis base adduct of B(2)pin(2) and the NHC (1,3-bis(cyclohexyl)imidazol-2-ylidene), which was proposed to act as a source of nucleophilic boryl groups in the β-borylation of α,β-unsaturated ketones, has been isolated, and its solid state structure and solution behavior was studied. In solution, the binding is weak, and NMR spectroscopy reveals a rapid exchange of the NHC between the two boron centers. DFT calculations reveal that the exchange involves dissociation and reassociation of NHC rather than an intramolecular process.

Reaction of [(IPr)Cu-OtBu] (1) with pinB-SiMe(2)Ph (2) leads to the Cu-silyl complex [(IPr)Cu-SiMe(2)Ph] (3). Insertion of CO(2) into the Cu-Si bond of 3 is followed by transformation of the resulting silanecarboxy complex [(IPr)Cu-O(2)CSiMe(2)Ph] (4) to the silanolate complex [(IPr)Cu-OSiMe(2)Ph] (5) via extrusion of CO. As 5 reacts readily with 2 to regenerate 3, a catalytic CO(2) reduction to CO is feasible. The individual steps were studied by in situ(13)C NMR spectroscopy of a series of stoichiometric reactions. Complexes 3, 4, and 5 were isolated and fully characterized, including single-crystal X-ray diffraction studies. Interestingly, the catalytic reduction of CO(2) using silylborane 2 as a stoichiometric reducing agent leads not only to CO and pinB-O-SiMe(2)Ph but also to PhMe(2)Si-CO(2)-SiMe(2)Ph as an additional reduction product.

Activation of the Si-B inter-element bond with copper(I) alkoxides produces copper-based silicon nucleophiles that react readily with aldehydes to yield α-silyl alcohols (that is, α-hydroxysilanes) after hydrolysis. Two independent protocols were developed, one employing a well-defined NHC-CuOtBu complex and one using the simple CuCN-NaOMe combination without added ligand. The mechanism of the aldehyde addition was investigated in detail by stoichiometric and catalytic experiments as well as NMR spectroscopic measurements. The primary reaction product of the addition of the Si-B reagent and the aldehyde (a boric acid ester of the α-silyl alcohol) and also the "dead-end" intermediate, formed in the competing [1,2]-Brook rearrangement, were characterized crystallographically. Based on these data, a reasonable catalytic cycle is proposed. The NHC-CuOtBu catalytic setup performs nicely at elevated temperature. A more reactive catalytic system is generated from CuCN-NaOMe, showing fast turnover at a significantly lower temperature. Both aromatic and aliphatic aldehydes are transformed into the corresponding α-silyl alcohols in good to very good yields under these mild reaction conditions., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A novel sp(2)-sp(3) diboron reagent has been developed for the copper-catalyzed β-boration of α,β-unsaturated conjugated compounds. The reaction proceeds under mild conditions with various substrates, i.e., α,β-unsaturated esters, ketones, nitriles, ynones, amides, and aldehydes, in the absence of additives such as phosphine and sodium tert-butoxide to provide β-borylhomoenolates in good to excellent yields. The presence of an sp(3)-hybridized boron center, unambigously confirmed by X-ray crystallography, sufficiently activates the unsymmetrical pinacolato diisopropanolaminato diboron (PDIPA diboron, 2) to transfer the sp(2)-hybridized boron moiety chemoselectively. These observations suggest that the activation of one of the boron atoms is an essential step in the Cu-catalyzed β-boration catalytic cycle.

We address the adsorption of asymmetric Pd pincer complexes on a Cu(111) surface by scanning tunneling microscopy. The structural asymmetry is manifested in the observation of two chiral enantiomers. To enable an unambiguous identification of individual constituents, three closely related complexes with small modifications are investigated in parallel. Thereby, methyl substituents determine attractive molecule-molecule interaction. Depending on their distribution, dimerization and tetramerization can be observed.

The indenyl compound (eta(5)-C(9)H(7))Rh(coe)(2) (1, coe = cis-cyclooctene) has been prepared as a thermally stable alternative to the diethylene derivative (eta(5)-C(9)H(7))Rh(eta(2)-H(2)C[double bond, length as m-dash]CH(2))(2). Compound 1 reacts with unsaturated phosphines Ph(2)PR (R = CH[double bond, length as m-dash]CH(2), 2; CH(2)CH=CH(2), 3; and C triple bond C-tert-Bu, 4) to give complexes of the type (eta(5)-C(9)H(7))Rh(Ph(2)PR)(2), where bonding occurs through the phosphorus atom. Addition of Ph(2)PC triple bond CPPh(2) to 1 gave the dimer [(eta(5)-C(9)H(7))Rh(micro-Ph(2)PC triple bond CPPh(2))](2) (5). Solution and solid state data showed that these new phosphine complexes have only a moderate amount of distortion within the indenyl ring. These compounds were found to catalyse the hydroboration of vinylarenes and the first example of an internal hydroboration of diphenylvinylphosphine has been reported.

A simple but effective copper-catalyzed borylation of aryl halides, including electron-rich and sterically hindered aryl bromides, with alkoxy diboron reagents occurs under mild conditions (see scheme). Preliminary DFT studies of the mechanism suggest that sigma-bond metathesis between a copper-boryl intermediate and the aryl halide generates the aryl boronate product.

Unsymmetrical 1-(arylimino)-3-(2-hetarylimino)isoindolines have been prepared from 1,3-diiminoisoindoline, an arylamine (aniline, 2-methylaniline, 2-iodoaniline), and a heteroaromatic amine (2-amino-6-methylpyridine, 2-amino-4-methylthiazole) in a stepwise manner by two consecutive condensations. The metalation reactions of these compounds with palladium(II) acetate proceed upon cyclopalladation of the carbocyclic aryl moieties and yield unsymmetrical C, N, N pincer complexes in all cases. X-ray crystallographic analysis were performed on single crystals of hydrogen{acetato[1-phenylimino-3-(6-methylpyridylimino)isoindolinato]palladate(II)} H[(phpi)Pd(OAc)] and pyridine[1-(2-tolylimino)-3-(4-methylthiazolylimino)isoindolinato]palladium(II) [(2-tolti)Pd(py)] by which the coordination mode, the conformation, the protonation site, and the trans influence of the carbon donor were established. For one more C, N, N pincer complex, hydrogen{acetato[1-(2-iodophenylimino)-3-(6-methylpyridylimino)isoindolinato]palladate(II)} H[(2-Iphpi)Pd(OAc)], a similar mononuclear coordination mode was confirmed by (1)H NMR spectroscopy, whereas for the product of an oxidative addition reaction of a palladium(0) precursor to the iodoaryl derivative a product with exo coordination was found. First experiments showed the effectivity of one of these complexes as a precatalyst in CC coupling reactions (Heck and Stille coupling).

The treatment of bis(4-tert-butylthiazolyl)isoindoline (4-tBuBTI) with palladium acetate results in the exclusive formation of an organometallic PdII compound with C-H activated t-butyl group and a hemilabile S-coordinated thiazole donor in cis-position.

Four new dimeric bis(BF(2))-2,2'-bidipyrrins (bisBODIPYs), and their corresponding BODIPY monomers, have been prepared and studied with respect to their structural and photophysical properties. The solid-state molecular structure of the dimers and the relative orientation of the subunits have been revealed by an X-ray diffraction study, which showed that the molecules contain two directly linked BODIPY chromophores in a conformationally fixed, almost orthogonal arrangement. Two of the fluorine atoms are in close contact with each other and the (19)F NMR spectra show a characteristic through-space coupling in solution. The new chromophores all exhibit a clear exciton splitting in the absorption spectra with maxima at about 490 and 560 nm, and are highly luminescent with an intense emission band at around 640 nm. The Stokes shift, which is the difference between the maximum of the lowest-energy absorption band and the maximum of the emission band, has a typical value of 5 to 15 nm for simple BODIPYs, whereas this value increases to 80 nm or more for the dimers, along with a slight decrease in fluorescence quantum yields and lifetimes. These properties indicate potential uses of these new fluorophoric materials as functional dyes in biomedical and materials applications and also in model compounds for BODIPY aggregates.

In the crystal structure of the title compound, C(8)H(11)NO(2), three distinct molecules are present in the asymmetric unit. The molecules are organized in two different hydrogen-bonded tapes, which form a complex layered structure. A structural comparison with the crystal structures of related maleimide derivatives unravels a stepwise evolution of morphological complexity with increasing molecular complexity for this class of compounds.

The reaction of 1,3-bis(4,6-dimethylpyridyl-2-imino)isoindoline and palladium acetate in methanol selectively yields the expected acetato palladium N,N,N-chelate or a cyclometalated tetranuclear dimer depending on the stoichiometry of the reactants.

Purpose: This trial was conducted to determine whether high-dose fluorouracil (FU) given as a weekly 24-hour infusion is more active than bolus FU + leucovorin (LV), and whether high-dose infusional FU can be modulated by LV., Patients and Methods: A total of 497 patients with previously untreated metastatic colorectal cancer were randomly assigned to receive bolus FU 425 mg/m2 intravenously + LV 20 mg/m2 on days 1 to 5 and repeated on day 28 (FU + LV), or FU 2600 mg/m2 as a 24-hour infusion alone (FU24h) or in combination with 500 mg/m2 LV (FU24h + LV)-all given weekly x6 followed by a 2-week rest period. Survival was the major study end point., Results: With a median follow-up of more than 3 years, survival did not differ among the treatment groups (median FU + LV, 11.1 months [95% CI, 10.2 to 15.0 months]; FU24h, 13.0 months [95% CI, 10.4 to 15.4 months]; FU24h + LV, 13.7 months [95% CI, 12.0 to 16.4 months]; P =.724). Progression-free survival (PFS) was significantly longer for FU24h + LV (median FU + LV, 4.0 months [95% CI, 3.4 to 4.9]; FU24h, 4.1 months [95% CI, 3.4 to 5.0]; FU24h + LV 5.6 months [95% CI, 4.4 to 6.7]; P =.029). The response rates in the subgroup of patients with measurable disease were 12%, 10%, and 17% for FU + LV, FU24h, and FU24h + LV, respectively (not significant). Occurrence of grade 3 and 4 diarrhea was higher in the FU24h + LV arm (22%) compared with the FU24h (6%) or FU + LV (9%) arms; however, stomatitis (11% in FU + LV v 3% in FU24h v 5% in FU24h + LV arms) and hematologic toxicity were higher in the bolus FU + LV arm. Global quality of life did not differ within the three arms., Conclusion: Neither FU24h + LV nor FU24h prolong survival, relative to bolus FU + LV. Leucovorin increases PFS if added to FU24h, but increases toxicity.