Search results for "Clusters"
showing 10 items of 1274 documents
Highly Robust but Surface-Active : An N-Heterocyclic Carbene-Stabilized Au25 Nanocluster
2019
Surface organic ligands play a critical role in stabilizing atomically precise metal nanoclusters in solutions. However, it is still challenging to prepare highly robust ligated metal nanoclusters that are surface-active for liquid-phase catalysis without any pre-treatment. Now, an N-heterocyclic carbene-stabilized Au25 nanocluster with high thermal and air stabilities is presented as a homogenous catalyst for cycloisomerization of alkynyl amines to indoles. The nanocluster, characterized as [Au25(iPr2-bimy)10Br7]2+ (iPr2-bimy=1,3-diisopropylbenzimidazolin-2-ylidene) (1), was synthesized by direct reduction of AuSMe2Cl and iPr2-bimyAuBr with NaBH4 in one pot. X-ray crystallization analysis …
MULTI-OBJECTIVE OPTIMISATION OF BUILDINGS AND BUILDING CLUSTERS PERFORMANCE: A LIFE CYCLE THINKING APPROACH
2021
Acid–Base Properties and Surface Charge Distribution of the Water-Soluble Au102(pMBA)44 Nanocluster
2016
The pKa of the p-mercaptobenzoic acid (pMBA) ligands in the Au102(pMBA)44 nanocluster was measured by using acid–base and IR titration. The observed macroscopic pKa = 6.18 ± 0.05 is significantly more basic than that of free pMBA (pKa = 4.16), and the protonation behavior is anticooperative according to the Hill coefficient n = 0.64 ± 0.04. The cluster is truly water-soluble when more than 22 and insoluble when fewer than 7 ligands are in the deprotonated state. In order to obtain more insight into the anticooperative character, the cluster was modeled at pH ∼6.2 using constant pH molecular dynamics simulations. The pKa values of the individual pMBAs are in the range of 5.18–7.58, depending…
The accuracy of molecular dipole moments in standard electronic structure calculations
2000
Abstract A systematic investigation has been carried out of the accuracy of calculated molecular equilibrium dipole moments of 11 polar closed-shell molecules, using the HF, MP2, CCSD and CCSD(T) models and correlation-consistent basis sets. Augmented basis sets are important for improving the basis-set convergence, but the quality of the results depends more on the correlation treatment than on the cardinal number of the basis set. Augmented triple-zeta basis sets are sufficient for most calculations. The mean absolute error of the HF calculations is 0.16 D, which is reduced at the MP2 and CCSD levels to 0.048 and 0.025 D, respectively. The CCSD(T) errors are small – typically
Gold Nanoclusters: Atomically Precise Gold Nanoclusters: Towards an Optimal Biocompatible System from a Theoretical–Experimental Strategy (Small 27/2…
2021
An ab initio potential energy surface for the C2H2-N2 system
2012
International audience; An ab initio potential energy surface determined at the CCSD(T) level of theory is presented for the van der Waals complex C2H2-N2. Additional calculations performed with the HF- and DFT-SAPT methods compare well with the CCSD(T) results and allow a better understanding of the main features of this interaction potential surface. An expansion of this surface over spherical harmonics has also been performed. The global energy minimum of the complex is obtained for the linear conformation. The T conformations are the least attractive. Such characteristics mainly arise because of the variation, in sign and in absolute value of the electrostatic energy between all these c…
Biosynthesis of heterocycles: From isolation to gene cluster
2015
This book describes biosynthetic methods to synthesize heterocyclic compounds, offering a guide for the development of new drugs based on natural products. The authors explain the role of natural products in chemistry and their formation along with important analytical methods and techniques for working with heterocycles. Covers methods and techniques: isotopic labelling, enzymes and mutants, and pathway identification. Provides a thorough resource of information specifically on heterocyclic natural products and their practical biosynthetic relevance. Explains the role of natural products in chemistry and their formation. Discusses gene cluster identification and the use of biogenetic engin…
Dipole Moments and the Direction of the Transition Dipole Moment of Some Intramolecular Exciplexes
1988
The dipole moments of some intramolecular exciplex systems have been determined from the effect of an electric field on their fluorescence and are compared to those estimated from solvent shift measurements. The charge transfer between the donor and acceptor subunits is between 0.6 and 0.9 of a full charge transfer. The face-to-face type exciplexes show considerable deviations from the general behaviour what might be due to some admixture of locally excited configurations to the exciplex wave function, in this way reducing the dipole moment values and changing the direction of the transition dipole moment.
Aza-BODIPY: A New Vector for Enhanced Theranostic Boron Neutron Capture Therapy Applications
2020
Boron neutron capture therapy (BNCT) is a radiotherapeutic modality based on the nuclear capture of slow neutrons by stable 10B atoms followed by charged particle emission that inducing extensive damage on a very localized level (<
Co-creation for Digitalization: A Study of Co-creation in Norwegian Business Clusters
2020
Part 2: Fourth Industrial Revolution; International audience; There is a growing emphasis on digitalization in research and business practice. The rapid progress in digital technologies compel firms to innovate and transform their businesses. One way to improve the capacity to innovate and transform is to cooperate with others. However, there is a general lack of research on how co-creation among businesses can facilitate digitalization. This qualitative study explores how co-creation among businesses can stimulate and facilitate digitalization.We have investigated co-creation activities involving companies in business clusters. This paper reports from a study of three business clusters in …