Quenched Lewis Acidity: Studies on the Medium Dependent Fluorescence of Zinc(II) Complexes

Abstract

Three new zinc(II) coordination units [Zn(1-3)] based on planar-directing tetradentate Schiff base-like ligands H 2 (1-3) were synthesized. Their solid-state structures were investigated by single crystal X-ray diffraction, showing the tendency to overcome the square-planar coordination sphere by axial ligation. Affinity in solution towards axial ligation has been tested by extended spectroscopic studies, both in the absorption and emission mode. The electronic spectrum of the pyridine complex [Zn(1)(py)] has been characterized by MC-PDFT to validate the results of extended TD-DFT studies. Green emission of non-emissive solutions of [Zn(1-3)] in chloroform could be switched on in the presence of potent Lewis-bases. While interpretation in terms of an equilibrium of stacked/non-fluorescent and destacked/fluorescent species is in line with precedents from literature, the sensitivity of [Zn(1-3)] was greatly reduced. Results of a computationbased structure search allow to trace the hidden Lewis acidity of [Zn(1-3)] to a new stacking motif, resulting in a strongly enhanced stability of the dimers.

Self‐Assembled Fluorescent Block Copolymer Micelles with Responsive Emission

“…Despite the low effective pyridine concentration in the molecularly dissolved form, still a non‐negligible amount of potentially coordinative pyridine units is present, which interferes with the aimed off–on behavior of the sensor. We reported previously on the close‐to‐zero emission of the ligand H 2 (L) in both solvents, CHCl 3 and pyridine [12] . To obtain a sharp off–on emission, we used acidified chloroform to consciously disrupt the parent zinc(II) complex to form the free ligand H 2 (L) and a soluble but not further defined zinc(II) species, according to: [Zn(L)] +2 H + → H 2 (L) +*Zn 2+ * [12] .…”

Selbstassemblierte fluoreszierende Blockcopolymer‐Mizellen mit responsiver Emission

“…Dabei wurde ein "Einschalten" der Emission bei Zugabe von Pyridin beobachtet. [12] Da sich die Fluoreszenz der [Zn(L)]@BCP-Komposite thermisch als bemerkenswert stabil erwies, stellte sich zum einen die Frage ob die Mizellenform für die starke Emission essentiell ist. Zum anderen stellte sich die Frage, ob diese Materialien einen Zugang zu medienresponsiven Sensormaterialien bieten, deren Emission durch extern stimulierte Selbstassemblierung ausgelöst werden kann.…”

“…Im Gegensatz dazu wird eine intensive grüne Emission in koordinierenden Lösungsmitteln aufgrund von koordinations-induzierter Entstapelung beobachtet. [11,12] In diesem…”

Cooperative Effects in Heterometallic Complexes

“…The current special issue of Chemistry -a European Journal issue comprises 23 contributions in total, 17 of which stem from work that was conducted within the framework of the 3MET.de center, [1][2][3][4]6,[8][9][10][11]14,[16][17][18][19][20][21]23] and six from outside. [5,7,12,13,15,22] There are two reviews: one is focused on elucidating the magnetic benefits and challenges of cooperativity within 3d-4f based coordination clusters of archetypical butterfly type, [21] and the other one highlights more generally the advancement of inorganic coordination chemistry by spectroscopy of isolated molecules in view of the applied methods and the achieved applications. [18] Three communications, [3,12,22] one concept article [8] and 17 full papers [1,2,[4][5][6][7][9][10][11][13][14][15][16][17]19,20,23...…”

“…[5,7,12,13,15,22] There are two reviews: one is focused on elucidating the magnetic benefits and challenges of cooperativity within 3d-4f based coordination clusters of archetypical butterfly type, [21] and the other one highlights more generally the advancement of inorganic coordination chemistry by spectroscopy of isolated molecules in view of the applied methods and the achieved applications. [18] Three communications, [3,12,22] one concept article [8] and 17 full papers [1,2,[4][5][6][7][9][10][11][13][14][15][16][17]19,20,23] document and discuss particular 3MET species and their relevance for our understanding of the TM interactions within. A contribution on the development and application of a complete active space spin-orbit configuration interaction program designed for molecule magnets deserves special mention: this manuscript appears in a more specialized sister journal.…”