TY - JOUR A1 - Otto, S. A1 - Grabolle, Markus A1 - Förster, C. A1 - Kreitner, C. A1 - Resch-Genger, Ute A1 - Heinze, K. T1 - [Cr(ddpd)2]3+: A molecular, water-soluble, highly NIR-emissive ruby analogue N2 - Bright, long-lived emission from first-row transition-metal complexes is very challenging to achieve. Herein, we present a new strategy relying on the rational tuning of energy levels. With the aid of the large N-Cr-N bite angle of the tridentate ligand ddpd (N,N′-dimethyl-N,N′-dipyridine-2-ylpyridine-2,6-diamine) and its strong σ-donating capabilities, a very large ligand-field splitting could be introduced in the chromium(III) complex [Cr(ddpd)2]3+, that shifts the deactivating and photoreactive 4T2 state well above the emitting 2E state. Prevention of back-intersystem crossing from the 2E to the 4T2 state enables exceptionally high near-infrared phosphorescence quantum yields and lifetimes for this 3d metal complex. The complex [Cr(ddpd)2](BF4)3 is highly water-soluble and very stable towards thermal and photo-induced substitution reactions and can be used for fluorescence intensity- and lifetime-based oxygen sensing in the NIR. KW - Chromium complexes KW - Intersystem crossing KW - Ligand-field splitting KW - NIR luminescence KW - Photophysics PY - 2015 U6 - https://doi.org/10.1002/anie.201504894 SN - 1433-7851 SN - 1521-3773 SN - 0570-0833 VL - 54 IS - 39 SP - 11572 EP - 11576 PB - Wiley-VCH CY - Weinheim AN - OPUS4-35084 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wang, Cui A1 - Otto, S. A1 - Dorn, M. A1 - Kreidt, E. A1 - Lebon, J. A1 - Sršan, L. A1 - Di Martino-Fumo, P. A1 - Gerhards, M. A1 - Resch-Genger, Ute A1 - Seitz, M. A1 - Heinze, K. T1 - Deuterated molecular ruby with record luminescence quantum yield N2 - The recently reported luminescent chromium(III) complex 13+ ([Cr(ddpd)2]3+; ddpd=N,N’-dimethyl-N,N’-dipyridine-2-yl-pyridine-2,6-diamine) shows exceptionally strong near-IR emission at 775 nm in water under ambient conditions (F=11%) with a microsecond lifetime as the ligand design in 13+ effectively eliminates non-radiative decay pathways, such as photosubstitution, back-intersystem crossing, and trigonal twists. In the absence of energy acceptors, such as dioxygen, the remaining decay pathways are energy transfer to high energy solvent and ligand oscillators, namely OH and CH stretching vibrations. Selective deuteration of the solvents and the ddpd ligands probes the efficiency of these oscillators in the excited state deactivation. Addressing these energytransfer pathways in the first and second coordination sphere furnishes a record 30% quantum yield and a 2.3 millisecond lifetime for a metal complex with an earth-abundant metal ion in solution at room temperature. The combined fundamental insights will pave the way for selective design strategies in the field of luminescent complexes with earth-abundant metal ions. KW - Record luminescence quantum yield KW - Phorsphorescence KW - Cr-complex KW - Lifetime PY - 2018 U6 - https://doi.org/10.1002/ange.201711350 U6 - https://doi.org/10.1002/anie.201711350 SN - 1521-3773 VL - 57 IS - 4 SP - 1112 EP - 1116 PB - Wiley-VCH Verlag & Co. KGaA CY - Weinheim AN - OPUS4-45085 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wang, Cui A1 - Otto, S. A1 - Dorn, M. A1 - Kreidt, E. A1 - Lebon, J. A1 - Sršan, L. A1 - Di Martino-Fumo, P. A1 - Gerhards, M. A1 - Seitz, M. A1 - Resch-Genger, Ute A1 - Heinze, K. T1 - Deuterierter molekularer Rubin mit Rekord-Lumineszenzquantenausbeute N2 - Der kürzlich publizierte Chrom(III)-Komplex 13+([Cr(ddpd)2]3+) zeigt in wässriger Lösung unter Umgebungsbedingungen eine bemerkenswert starke Emission im nahen Infrarot-Bereich mit einer Emissionswellenlänge von 775 nm. Geschicktes Ligandendesign verhindert strahlungslose Desaktivierungsprozesse wie Photosubstitution, Rück-Intersystem-Crossing und trigonale Verzerrungen und führt damit zu einer Phosphoreszenzlebensdauer im Bereich von Mikrosekunden. In Abwesenheit von Energieakzeptoren wie molekularem Sauerstoff verbleibt nur Energietransfer zu hochenergetischen Oszillatoren der Liganden und Lösungsmittelmoleküle wie beispielsweise OH- und CH-Streckschwingungen als Desaktivierungspfad. Selektive Deuterierung der ddpd-Liganden und der Lösungsmittel l-sst die Effizienz dieser Oszillatoren bei der Desaktivierung angeregter Zustände erkennbar werden. Gezieltes Ausschalten dieser Relaxationspfade führt zu einer Quantenausbeute von 30% und einer Lebensdauer von 2.3 Millisekunden bei Raumtemperatur in Lösung – Rekordwerte für einen Komplex, der auf dem Element Chrom basiert. Diese fundamentalen Erkenntnisse ebnen den Weg für gezieltes Ligandendesign zur Synthese lumineszierender Komplexe mit gut verfügbaren Übergangsmetallen. KW - Cr(III)-Komplex KW - Rekord Luminescence Quantum Ausbeute KW - Abklingzeit PY - 2018 U6 - https://doi.org/10.1002/ange.201711350 SN - 1521-3757 VL - 130 IS - 4 SP - 1125 EP - 1130 PB - Wiley-VCH Verlag & Co. KGaA CY - Weinheim AN - OPUS4-45086 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Otto, S. A1 - Moll, J. A1 - Förster, C. A1 - Geißler, Daniel A1 - Wang, Cui A1 - Resch-Genger, Ute A1 - Heinze, K. T1 - Three-in-One Crystal: The Coordination Diversity of Zinc Polypyridine Complexes N2 - The syntheses, structures, and photophysical properties of two new zinc(II) complexes bearing the tridentate N,N′-dimethyl-N,N′-dipyridin-2-ylpyridine-2,6-diamine (ddpd) ligand are presented. Structural investigations through single-crystal X-ray diffractometry, NMR spectroscopy, and density functional theory calculations revealed a diverse coordination behavior that depends on the counterion. Spectroscopic (UV/Vis and emission spectroscopy) and theoretical techniques (DFT and time-dependent DFT calculations) were employed to explore the photophysical properties of the complexes. KW - Zinc(II) complexes KW - X-ray diffractometry (XRD) KW - NMR spectroscopy KW - Density functional theory (DFT) KW - UV/Vis and emission spectroscopy PY - 2017 U6 - https://doi.org/10.1002/ejic.201700948 SN - 1434-1948 SN - 1099-0682 VL - 43 SP - 5033 EP - 5040 PB - WILEY-VCH Verlag GmbH & Co. KGaA CY - Weinheim AN - OPUS4-43274 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wang, Cui A1 - Otto, S. A1 - Dorn, M. A1 - Heinze, K. A1 - Resch-Genger, Ute T1 - Luminescent TOP nanosensors for simultaneously measuring temperature, oxygen, and pH at a single excitation wavelength N2 - Two nanosensors for simultaneous optical measurements of the bioanalytically and biologically relevant analytes temperature (“T”), oxygen (“O”), and pH (“P”) have been designed. These “TOP” nanosensors are based on 100 nmsized silica-coated polystyrene nanoparticles (PS-NPs) doped with a near-infrared emissive oxygen- and temperature-sensitive chromium(III) complex ([Cr(ddpd)2][BPh4]3, CrBPh4) and an inert reference dye (Nile Red, NR or 5,10,15,20tetrakis(pentafluorophenyl) porphyrin, TFPP) and are covalently labeled with pHsensitive fluorescein isothiocyanate (FITC). These emitters can be excited at the same wavelength and reveal spectrally distinguishable emission bands, allowing for ratiometric intensity-based and time-resolved studies in the visible and near-infrared wavelength region. Studies in PBS buffer solutions and in a model body liquid demonstrate the applicability of these nanosensors for the sensitive luminescence readout of TOP simultaneously at the same spatialposition. KW - Medical diagnostics KW - Sensor KW - Nanoparticle KW - Fluorescence KW - Nanosensor KW - Oxygen KW - Temperature KW - pH KW - Ratiometric KW - Lifetime KW - NIR KW - Cr(III) complex KW - Dye KW - FITC KW - Environment PY - 2019 U6 - https://doi.org/10.1021/acs.analchem.8b05060 SN - 0003-2700 VL - 91 IS - 3 SP - 2337 EP - 2344 PB - ACS AN - OPUS4-47455 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Otto, S. A1 - Förster, C. A1 - Wang, Cui A1 - Resch-Genger, Ute A1 - Heinze, K. T1 - A Strongly Luminescent Chromium(III) ComplexAcid N2 - The synthesis, structure, reactivity,and photophysical properties of anovel acidic,luminescentchromium(III) complex [Cr(H2tpda)2]3+ (23+ +)bearing the tridentate H2tpda (2,6-bis(2-pyridylamino)pyridine) ligand are presented. Excitation of 23+ + at 442 nm results in strong, long-lived NIR luminescence at 782 nm in water and in acetonitrile. X-ray diffraction analysis and IR spectroscopy revealhydrogen-bonding interactions of the counter ions to the NH groups of 23+ + in the solidstate. Deprotonation of the NH groups of 23+ + by using anon-nucleophilic Schwesinger base in CH3CN switches off the luminescence. Re-protonation by using HClO4 restores the emission. In water,the pKa value of 23+ + amountsto8 .8, yet deprotonation is not reversible in the presence of hydroxide ions. Dioxygen quenches the emission of 23+ +,but to aweaker extent than expected. This is possibly due to the strong ion-pairing properties of 23+ + even in solution, reducing the energy transfer efficiency to O2.Deuteration of the NH groups of 23+ + approximately doubles the quantum yield and lifetime in water,demonstrating the importance of multiphoton relaxation in these NIR emitters. KW - Cr(III) complex KW - Oxygen sensor KW - pH sensor KW - Luminescence KW - Luminescence lifetime KW - Quantum yield KW - NIR emitter PY - 2018 U6 - https://doi.org/10.1002/chem.201802797 SN - 0947-6539 VL - 24 IS - 48 SP - 12555 EP - 12563 PB - Wiley‐VCH Verlag GmbH & Co. KGaA CY - Weinheim AN - OPUS4-45929 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -