35 research outputs found
Synthesis, Structure and Bonding Analysis of the Zwitterionic PPP-Pincer Complex (6-Ph2P-Ace-5-)2P(O)AuCl2
The reaction of (6-Ph2P-Ace-5-)2P(O)H with (tht)AuCl3proceeds via elimination oftetrahydrothiophene (tht) and HCl, providing the zwitterionic PPP-pincer complex (6-Ph2P-Ace-5-)2P(O)AuCl2(1) as yellow crystals. The molecular structure of1was established and studied by X-raycrystallography. The electronic structure was computationally analyzed using a comprehensiveset of real-space bonding indicators derived from electron and electron-pair densities, providinginsight into the relative contributions of covalent and non-covalent forces to the polar-covalent AuâCl,AuâP, and PâOâbonds; the latter being one of the textbook cases for strongly polarized covalentinteractions. Partial spatial complementarity between both bonding aspects is suggested by theelectronic properties of the distinctively different AuâCl bonds
Forecast reconciliation for vaccine supply chain optimization
Vaccine supply chain optimization can benefit from hierarchical time series
forecasting, when grouping the vaccines by type or location. However, forecasts
of different hierarchy levels become incoherent when higher levels do not match
the sum of the lower levels forecasts, which can be addressed by reconciliation
methods. In this paper, we tackle the vaccine sale forecasting problem by
modeling sales data from GSK between 2010 and 2021 as a hierarchical time
series. After forecasting future values with several ARIMA models, we
systematically compare the performance of various reconciliation methods, using
statistical tests. We also compare the performance of the forecast before and
after COVID. The results highlight Minimum Trace and Weighted Least Squares
with Structural scaling as the best performing methods, which provided a
coherent forecast while reducing the forecast error of the baseline ARIMA
Emission color-tunable oxazol(in)yl-substituted excited-state intramolecular proton transfer (ESIPT)-based luminophores
Oxazolinyl- and arylchalcogenazolyl-substituted hydroxyfluorenes exhibiting excited-state intramolecular proton transfer (ESIPT) are described as potent and highly modular luminophores. Emission color tuning was achieved by varying the Ï-expansion and the insertion of different chalcogen atoms
Lewis Superacidic Divalent Bis( m âterphenyl)element Cations [(2,6âMes 2 C 6 H 3 ) 2 E] + of Group 13 Revisited and Extended (E=B, Al, Ga, In, Tl)
In a combined experimental and computational study, the
molecular and electronic structures of the divalent bis(m-
terphenyl)element cations [(2,6-Mes2C6H3)2E]+ of group 13 (1,
E=B; 2, E=Al; 3, E=Ga; 4, E=In; 5, E=Tl) were investigated. The
preparation and characterization of 2, 3 and 5 were previously
reported by Wehmschulteâs (Organometallics 2004, 23, 1965â
1967; J. Am. Chem. Soc. 2003, 125, 1470â1471) and our groups
(Organometallics 2009, 28, 6893â6901). The indinium ion 4 was
prepared and fully characterized for the first time. Attempts to
prepare the borinium ion 1 by fluoride or hydride abstraction
were unsuccessful. The electronic structures of 1â5 and the
stabilization by the bulky m-terphenyl substituents were
analyzed using quantum chemical calculations and compared
to the divalent bis(m-terphenyl)pnictogenium ions [(2,6-
Mes2C6H3)2E]+ of group 15 (6, E=P; 7, E=As; 8, E=Sb; 9, E=Bi)
previously investigated by our group (Angew. Chem. Int. Ed.
2018, 57, 10080â10084). The calculated fluoride ion affinities
(FIA) of 1â9 are higher than that of SbF5, which classifies them
as Lewis superacids
Kinetic Stabilization of Heavier Bis(m-terphenyl)pnictogen Phosphaethynolates
Kinetic stabilization using bulky m-terphenyl substituents is the key to the isolation of the diarylantimony and diarylbismuth phosphaethynolates (2,6-Mes2C6H3)2EPCO and the related N-heterocyclic carbene complexes (2,6-Mes2C6H3)2EP(O)C(IMe4) (E=Sb, Bi; IMe4=1,3,4,5-tetramethylimidazol-2-ylidene), which have been fully characterized crystallographically and spectroscopically. The experimental characterization was augmented by a DFT based real space bond indicator analysis of the electron density, including AIM, NCI, and ELI-D methods
Intramolecular Reaction of Transient Phosphenium and Arsenium Ions Giving Rise to Isolable 9-Phospha- and 9-Arsena-Fluorenium Ions
Transient phosphenium and arsenium ions, generated by fluoride abstraction from bis(m-terphenyl)fluoropnictogens, underwent intramolecular electrophilic attack prior to methyl group migration and gave rise to isolable 9-phospha- and 9-arsena-fluorenium ions
Synthesis and Single-Electron Oxidation of Bulky Bis(m-terphenyl)chalcogenides: The Quest for Kinetically Stabilized Radical Cations
Sterically encumbered bis(m-terphenyl)chalcogenides, (2,6-Mes2C6H3)2E (E=S, Se, Te) were obtained by the reaction of the chalcogen tetrafluorides, EF4, with three equivalents of m-terphenyl lithium, 2,6-Mes2C6H3Li. The single-electron oxidation of (2,6-Mes2C6H3)2Te using XeF2/K[B(C6F5)4] afforded the radical cation [(2,6-Mes2C6H3)2Te][B(C6F5)4] that was isolated and fully characterized. The electrochemical oxidation of the lighter homologs (2,6-Mes2C6H3)2E (E=S, Se) was irreversible and impaired by rapid decomposition
Isolation of an Antiaromatic 9-Hydroxy Fluorenyl Cation
Fluorenyl cations are textbook examples of 4Ï electron antiaromatic five-membered ring systems. So far, they were reported only as short-lived intermediates generated under superacidic conditions or by flash photolysis. Attempts to prepare a m-terphenyl acylium cation by fluoride abstraction from a benzoyl fluoride gave rise to an isolable 9-hydroxy fluorenyl cation that formed by an intramolecular electrophilic attack at a flanking mesityl group prior to a 1,2-methyl shift and proton transfer to oxygen
New crystal structures of alkali metal tetrakis(pentafluorophenyl)borates
The crystal structures of the salts [Li(1,2-F2C6H4)] [B(C6F5)4] (1) and Cs[B(C6F5)4] (2) comprise six Li···F contacts (1.965(3) â 2.312(3) Ă
) and twelve Cs···F contacts (3.0312(1) â 3.7397(2) Ă
), respectively, which are significantly shorter than the sum of van der Waals radii (3.29 and 4.90 Ă
)
Nitrile-Substituted 2-(Oxazolinyl)-Phenols: Minimalistic Excited-State Intramolecular Proton Transfer (ESIPT)-Based Fluorophores
Herein, we present minimalistic single-benzene, excited-state intramolecular proton transfer (ESIPT) based fluorophores as powerful solid state emitters. The very simple synthesis gave access to all four regioisomers of nitrile-substituted 2(oxazolinyl)phenols (MW = 216.1). In respect of their emission properties they can be divided into aggregation-induced emission enhancement (AIEE) luminophores (1-CN and 2-CN), dual state emission (DSE) emitters (3-CN) and aggregation-caused quenching (ACQ) fluorophores (4âCN). Remarkably, with compound 1-CN we discovered a minimalistic ESIPT based fluorophore with extremely high quantum yield in the solid state ΊF = 87.3% at λem = 491 nm. Furthermore, quantum yields in solution were determined up to ΊF = 63.0%, combined with Stokes shifts up till 11.300 cmâ1. Temperature dependent emission mapping, crystal structure analysis and time-dependent density functional theory (TDDFT) calculations gave deep insight into the origin of the emission properties.<br /