ORCID Profile
0000-0001-9490-0023
Current Organisations
KU Leuven
,
University of Michigan
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Publisher: CSIRO Publishing
Date: 2012
DOI: 10.1071/CH12054
Abstract: The alkynes HC≡CC6H2-2,6-Et2-4-C≡CC6H4-4-NO2 (4) and HC≡CC6H4-4-C≡CC6H2-2,6-Et2-4-C≡CC6H4-4-NO2 (6) and gold alkynyl complexes Au{C≡CC6H2-2,5-(OEt)2-4-C≡CC6H4-4-NO2}(PPh3) (7), Au(C≡CC6H2-2,6-Et2-4-C≡CC6H4-4-NO2)(PPh3) (8), and Au(C≡CC6H4-4-C≡CC6H2-2,6-Et2-4-C≡CC6H4-4-NO2)(PPh3) (9) have been synthesized. The linear optical properties and quadratic optical non-linearities of 7–9 have been measured, the latter by hyper-Rayleigh scattering at 1064 nm, and compared with data for the previously reported complexes Au(C≡CC6H4-4-NO2)(PPh3) (10) and Au(C≡CC6H4-4-C≡CC6H4-4-NO2)(PPh3) (11). The optical absorption maximum red-shifts and the first hyperpolarizabilities increase on π-system lengthening and on introduction of electron-releasing substituents on the π-bridge ring adjacent to the metal centre. The cubic non-linear optical properties of 1,4-{(PCy3)Au(C≡C)}2C6H4 (12) and {(PCy3)Au(C≡C-4-C6H4C≡C)}6C6 (13) have been assessed by wide spectroscopic range femtosecond Z-scan studies the maximal values of the imaginary component and the effective two-photon absorption cross-section increase markedly on proceeding from linear complex 12 to 6-fold-symmetric complex 13, an increase that is maintained when data are scaled by relative molecular weight.
Publisher: Elsevier BV
Date: 07-2013
Publisher: Wiley
Date: 31-10-2018
Abstract: Straightforward syntheses of bis[bis{1,2-bis(diphenylphosphino)ethane}ruthenium]-functionalized 1,3,5-triethynylbenzene-cored complexes via a methodology employing "steric control" permit facile formation of Y-shaped Sonogashira coupling products and distorted-H-shaped homo-coupled quadrupolar products. Cyclic voltammetric data from these products reveal two reversible metal alkynyl-localized oxidation processes for all complexes. The wavelengths of the linear optical absorption maxima are dominated by the nature of the peripheral alkynyl ligand rather than the substituent at the unique arm of the "Y" or at the quadrupolar complex "core". The quadratic optical nonlinearities of the Y-shaped complexes were assessed by the hyper-Rayleigh scattering technique at 800 nm and employing 100 fs light pulses introduction of donor NEt
Publisher: Elsevier BV
Date: 05-2011
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C4OB02507E
Abstract: We report the synthesis of four new cationic push–pull membrane probes based on a thiophene core and evaluate their photobiological properties.
Publisher: Oxford University Press (OUP)
Date: 07-2012
DOI: 10.1093/PHE/PHS014
Publisher: Elsevier BV
Date: 04-2010
Publisher: American Chemical Society (ACS)
Date: 19-03-2009
DOI: 10.1021/IC801953Z
Abstract: The syntheses of trans-[Ru(4,4'-C[triple bond]CC(6)H(4)C[triple bond]CC(6)H(4)NO(2))Cl(dppe)(2)] (19) and the systematically varied complexes trans-[Ru(4,4',4''-C[triple bond]CC(6)H(4)X(2)C(6)H(4)Y(2)C(6)H(4)NO(2))Cl(L(2))(2)] [L(2) = dppe, X(2) = C[triple bond]C, Y(2) = (E)-CH=CH (12), C[triple bond]C (18) L(2) = dppe, X(2) = (E)-CH=CH, Y(2) = C[triple bond]C (14), (E)-CH=CH (16) L(2) = dppm, X(2) = C[triple bond]C, Y(2) = (E)-CH=CH (13) L(2) = dppm, X(2) = (E)-CH=CH, Y(2) = C[triple bond]C (15), (E)-CH=CH (17)] are reported, the latter being donor-bridge-acceptor complexes varying in bridge composition by replacement of yne with E-ene linkages, together with their cyclic voltammetric data, linear optical, and quadratic nonlinear optical response data. Ru(II/III) oxidation potentials increase on replacing yne linkage by E-ene linkage at the phenylene adjacent to the metal center, and on replacing dppe by dppm co-ligands. The low-energy optical absorption maxima occur in the region 20,400-23,300 cm(-1) and are metal-to-ligand charge-transfer (MLCT) in origin these bands undergo a blue-shift upon pi-bridge lengthening by addition of phenyleneethynylene units, and on replacing E-ene linkages by yne linkages. Time-dependent density functional theory calculations on model complexes have suggested assignments for the low-energy bands. The optical spectra of selected oxidized species contain low-energy ligand-to-metal charge transfer (LMCT) bands centered in the region 9760-11,800 cm(-1). Quadratic molecular nonlinearities from hyper-Rayleigh scattering (HRS) studies at 1064 nm reveal an increase in the two-level-corrected beta(0) value on pi-bridge lengthening, a trend that is not seen with beta values because of the blue-shift in lambda(max) for this structural modification. Replacing yne linkages by E-ene linkage at the phenylene adjacent to the metal center or dppm co-ligand by dppe results in an increase in beta and beta(0) values. In contrast, quadratic molecular nonlinearities by HRS at 1300 nm or electric field-induced second-harmonic generation (EFISH) studies at 1907 nm do not afford clear trends.
Publisher: Elsevier BV
Date: 06-2020
Publisher: Wiley
Date: 09-05-2023
Abstract: Porphyrins are important macrocycles with applications in several areas including therapy, catalysis, and sensing. Strong nonlinear optical (NLO) responses are the key to fully exploiting the potential of these biocompatible molecules. We herein report that certain metal‐alkynyl donor/nitro acceptor‐functionalized porphyrins are attractive candidates for NLO applications. We show that specific ex les exhibit record quadratic optical nonlinearity, exceptional two‐photon absorption, and outstanding three‐photon absorption, and we report the first porphyrins that exhibit four‐photon absorption. The two‐, three‐, and four‐photon absorption maxima are found at the corresponding multiples of linear absorption bands that time‐dependent density functional theory assigns as admixtures of porphyrin‐localized π*←π and donor‐porphyrin to porphyrin‐acceptor charge‐transfer transitions.
Publisher: Elsevier BV
Date: 12-2012
Publisher: American Chemical Society (ACS)
Date: 19-04-2002
DOI: 10.1021/OM020008C
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D1NR08072E
Abstract: Qualitative different non-linear optical phenomena with high nonlinear cross sections, as measured using the z -scan technique in combination with a tunable nanosecond laser source, were found at different excitation wavelengths.
Publisher: Elsevier BV
Date: 07-2020
Publisher: American Chemical Society (ACS)
Date: 08-2006
DOI: 10.1021/JA062246V
Abstract: A combination of cyclic voltammetry (CV), UV-vis-NIR spectroscopy and spectroelectrochemistry, hyper-Rayleigh scattering (HRS) [including depolarization studies], Z-scan and degenerate four-wave mixing (DFWM) [including studies employing an optically transparent thin-layer electrochemical (OTTLE) cell to effect electrochemical switching of nonlinearity], pump-probe, and electroabsorption (EA) measurements have been used to comprehensively investigate the electronic, linear optical, and nonlinear optical (NLO) properties of nanoscopic pi-delocalizable electron-rich alkynylruthenium dendrimers, their precursor dendrons, and their linear analogues. CV, UV-vis-NIR spectroscopy, and UV-vis-NIR spectroelectrochemistry reveal that the reversible metal-centered oxidation processes in these complexes are accompanied by strong linear optical changes, "switching on" low-energy absorption bands, the frequency of which is tunable by ligand replacement. HRS studies at 1064 nm employing nanosecond pulses reveal large nonlinearities for these formally octupolar dendrimers depolarization measurements are consistent with lack of coplanarity upon pi-framework extension through the metal. EA studies at 350-800 nm in a poly(methyl methacrylate) matrix are consistent with the important transitions having a charge-transfer exciton character that increases markedly on introduction of peripheral polarizing substituent. Time-resolved pump-probe studies employing 55 ps, 527 nm pulses reveal absorption saturation, the longest excited-state lifetime being observed for the dendrimer. Z-scan studies at 800 nm employing femtosecond pulses reveal strong two-photon absorption that increases significantly on progression from linear complex to zero- and then first-generation dendrimer with no loss of optical transparency. Both refractive and absorptive nonlinearity for selected alkynylruthenium dendrimers have been reversibly "switched" by employing the Z-scan technique at 800 and 1180 nm and 100-150 fs pulses, together with a specially modified OTTLE cell, complementary femtosecond time-resolved DFWM and transient absorption studies at 800 nm suggesting that the NLO effects originate in picosecond time scale processes.
Publisher: Elsevier BV
Date: 04-2008
Publisher: SPIE
Date: 08-09-2011
DOI: 10.1117/12.892312
Publisher: Wiley
Date: 27-06-2023
Publisher: Elsevier BV
Date: 02-2006
Publisher: World Scientific Pub Co Pte Lt
Date: 03-1998
DOI: 10.1142/S0218863598000090
Abstract: Hyper-Rayleigh scattering is used to investigate the nonlinear optical properties of novel metal (ruthenium, nickel and gold) σ-arylacetylide complexes. The influence of the organometallic donor group and conjugating bridge on the quadratic hyperpolarizability is studied. For all organic ligands, the addition of the metal (donor) group is shown to increase the static hyperpolarizability by a factor of 2, 4 and 7 for gold, nickel and ruthenium complexes, respectively. Moreover, replacement of phenyl with a heterocyclic ring is demonstrated to enlarge the hyperpolarizability in the case of gold and ruthenium compounds.
Publisher: American Institute of Physics
Date: 2009
DOI: 10.1063/1.3203255
Publisher: SPIE
Date: 23-09-2016
DOI: 10.1117/12.2237203
Publisher: Oxford University Press (OUP)
Date: 06-05-2014
Abstract: We examine the perspectives of health promotion practitioners on their approaches to determining health promotion practice, in particular on the role of research and relationships in this process. Using Grounded Theory methods, we analysed 58 semi-structured interviews with 54 health promotion practitioners in New South Wales, Australia. Practitioners differentiated between relationship-based and research-based approaches as two sources of knowledge to guide health promotion practice. We identify several tensions in seeking to combine these approaches in practice and describe the strategies that participants adopted to manage these tensions. The strategies included working in an evidence-informed rather than evidence-based way, creating new evidence about relationship-based processes and outcomes, adopting 'relationship-based' research and evaluation methods, making research and evaluation useful for communities, building research and evaluation skills and improving collaboration between research and evaluation and programme implementation staff. We conclude by highlighting three systemic factors which could further support the integration of research-based and relationship-based health promotion practices: (i) expanding conceptions of health promotion evidence, (ii) developing 'relationship-based' research methods that enable practitioners to measure complex social processes and outcomes and to facilitate community participation and benefit, and (iii) developing organizational capacity.
Publisher: SPIE
Date: 30-04-2010
DOI: 10.1117/12.854664
Publisher: American Chemical Society (ACS)
Date: 15-12-2016
Publisher: Elsevier BV
Date: 02-2020
DOI: 10.1016/J.CARBPOL.2019.115496
Abstract: Chondroitin sulfates (CS) account for more than 80% of the glycosaminoglycans of articular cartilage, which impart its physiological functions. We quantified the absolute concentration of the CS components of the full thickness cartilages from the knees of patients with terminal-phase osteoarthritis. Osteochondrol biopsies were removed from the medial femoral condyle and lateral femoral condyle of sixty female patients received total knee arthroplasty, aged from 58 to 83 years old. We found the total CS concentrations and chondroitin-4-sulfate disaccharide were significantly lowered in osteoarthritic s les. Microstructure analysis indicated while chondroitin-0-sulfate was equally distributed across different zones of the osteoarthritic cartilages, chondroitin-4-sulfate is significantly less in the deep zones. Down-regulation of sulfotransferases, the enzymes responsible for CS sulfation, in the lesion site of cartilage were observed. Our study suggested chondroitin-4-sulfate down-regulation can be a diagnostic marker for degraded osteoarthritis cartilage, with potential implications in cartilage regeneration.
Publisher: Elsevier BV
Date: 07-2003
Publisher: Wiley
Date: 18-04-2018
Abstract: The syntheses of oligo(p-phenylene ethynylene)s (OPEs) end-functionalized by a nitro acceptor group and with a ligated ruthenium unit at varying locations in the OPE chain, namely, trans-[Ru{(C≡C-1,4-C
Publisher: Wiley
Date: 09-05-2023
Abstract: Porphyrins are important macrocycles with applications in several areas including therapy, catalysis, and sensing. Strong nonlinear optical (NLO) responses are the key to fully exploiting the potential of these biocompatible molecules. We herein report that certain metal‐alkynyl donor/nitro acceptor‐functionalized porphyrins are attractive candidates for NLO applications. We show that specific ex les exhibit record quadratic optical nonlinearity, exceptional two‐photon absorption, and outstanding three‐photon absorption, and we report the first porphyrins that exhibit four‐photon absorption. The two‐, three‐, and four‐photon absorption maxima are found at the corresponding multiples of linear absorption bands that time‐dependent density functional theory assigns as admixtures of porphyrin‐localized π*←π and donor‐porphyrin to porphyrin‐acceptor charge‐transfer transitions.
Publisher: Elsevier BV
Date: 04-2013
Publisher: Elsevier BV
Date: 2011
Publisher: American Chemical Society (ACS)
Date: 31-12-2002
DOI: 10.1021/JA028897I
Abstract: We have used several techniques, including hyper-Rayleigh scattering and Stark spectroscopy, to investigate the effects of polyene chain length on the optical properties of complexes containing ruthenium(II) electron donor groups and pyridinium electron acceptors. In marked contrast with all other known donor-acceptor polyenes, conjugation extension beyond a single double bond in the dipolar complexes studied leads to blue-shifting of the intramolecular charge-transfer absorptions. Furthermore, the static first hyperpolarizabilities beta0 become maximized with trans-1,3-butadienyl linkages and then decrease in complexes with three CH=CH bonds. Our results clearly demonstrate that the molecular engineering criteria for metal-containing nonlinear optical chromophores can differ dramatically from those for purely organic compounds.
Publisher: American Chemical Society (ACS)
Date: 06-07-2009
DOI: 10.1021/JA902793Z
Abstract: The syntheses of trans-[Ru{4,4'-C[triple bond]CC(6)H(2)[2,5-(OEt)(2)]C[triple bond]CC(6)H(4)NO(2)}Cl(dppm)(2)] (19), trans-[Ru{4,4',4''-C[triple bond]CC(6)H(4)C[triple bond]CC(6)H(2)[2,5-(OEt)(2)]C[triple bond]CC(6)H(4)NO(2)}Cl(dppm)(2)] (20), trans-[Ru{4,4',4'',4'''-C[triple bond]CC(6)H(4)C[triple bond]CC(6)H(2)[2,5-(OEt)(2)]C[triple bond]CC(6)H(2)[2,5-(OEt)(2)]C[triple bond]CC(6)H(4)NO(2)}Cl(dppe)(2)] (21), trans-[Ru{4,4',4'',4'''-C[triple bond]CC(6)H(4)C[triple bond]CC(6)H(2)[2,5-(OEt)(2)]C[triple bond]CC(6)H(2)[2,5-(OEt)(2)]C[triple bond]CC(6)H(4)NO(2)}Cl(dppm)(2)] (22), trans-[Ru{4,4',4'',4'''-C[triple bond]CC(6)H(4)C[triple bond]CC(6)H(4)C[triple bond]CC(6)H(2)[2,5-(OEt)(2)]C[triple bond]CC(6)H(4)NO(2)}Cl(dppm)(2)] (23), and trans-[Ru{4,4',4'',4''',4''''-C[triple bond]CC(6)H(4)C[triple bond]CC(6)H(4)C[triple bond]CC(6)H(2)[2,5-(OEt)(2)]C[triple bond]CC(6)H(2)[2,5-(OEt)(2)]C[triple bond]CC(6)H(4)NO(2)}Cl(dppm)(2)] (24) are reported, together with those of precursor alkynes, complexes with the donor-pi-bridge-acceptor formulation that affords efficient quadratic and cubic NLO compounds the identity of 19 was confirmed by a structural study. The electrochemical properties of 19-24 and related complexes with shorter pi-bridge ligands were assessed by cyclic voltammetry, and the linear optical, quadratic nonlinear optical, and cubic nonlinear optical properties were assayed by UV-vis-NIR spectroscopy, hyper-Rayleigh scattering studies at 1064 and 1300 nm, and broad spectral range femtosecond Z-scan studies, respectively. The Ru(II/III) oxidation potentials and wavelengths of the optical absorption maxima decrease on pi-bridge lengthening, until the tri(phenyleneethynylene) complex is reached, further chain lengthening leaving these parameters invariant theoretical studies employing time-dependent density functional theory have shed light on this behavior. The quadratic nonlinearity beta(1064) and two-photon absorption cross-section reach maximal values at this same pi-bridge length, a similar saturation behavior that may reflect a common importance of ruthenium-to-alkynyl ligand charge transfer in electronic and optical behavior in these molecules.
Publisher: SPIE
Date: 11-1996
DOI: 10.1117/12.256164
Publisher: Elsevier BV
Date: 07-2010
Publisher: Wiley
Date: 27-06-2023
Publisher: American Institute of Physics
Date: 2009
DOI: 10.1063/1.3203256
No related grants have been discovered for Koen Clays.