Chiral zinc(II) and cadmium(II) complexes with a dihydrophenanthroline ligand bearing (–)-α-pinene fragments: Synthesis, crystal structures and photophysical properties

Hybrid Inorganic–Organic Complexes of Zn, Cd, and Pb with a Cationic Phenanthro-diimine Ligand

“…The slightly distorted [CdBr 4 ] 2– tetrahedron is placed in voids formed by tetraarylphosphonium groups, which is apparently driven by the electrostatic attraction. The [ LP + CdBr 2 ] + cations dimerize via the nonsymmetrical bromide bridges (μ 2 -Br–Cd distances are 2.640(2), 2614(2), 2.861(2), and 2.802(2) Å; Table S2) that provides pentacoordinate environment of Cd­(II) ions and evidently follows a preference of [Cd­(diimine)­Hal 2 ] units to have a higher coordination number than that of Zn­(II) analogues. − …”

Efficient emission of Zn(ii) and Cd(ii) complexes with nopinane-annelated 4,5-diazafluorene and 4,5-diazafluoren-9-one ligands: how slight structural modification alters fluorescence mechanism

“…Interestingly, the similar dihydrophenanthroline ligand luminesces in the same region (λ max = 357 nm), but with twice less quantum efficiency (ϕ = 0.53). 124 The emission spectral shape of the complexes ZnLCl 2 and CdLCl 2 is similar to that for the free L ligand (Fig. 5, top); however, the vibrational satellite structure is less pronounced in the case of complexes.…”

“…122 The complexes with the limonene derivative demonstrate excitation wavelength-dependent emission with nanosecond and microsecond lifetimes of the excited states. Zinc(II) and cadmium(II) complexes with bipyridine-based ligands in which the pyridine groups are tied together by additional -CH 2 -CH 2and -CH 2bridges and feature peripheral (-)-α-pinene groups also appeared to be luminescent; 123,124 however, detailed photophysical studies were performed only for the -CH 2 -CH 2bridged compounds. According to these results, the photoluminescence quantum yields for the -CH 2 -CH 2bridged compounds reached several tens of percent.…”

Zn Coordination and the Identity of the Halide Ancillary Ligand Dramatically Influence the Excited-State Dynamics and Bimolecular Reactions of 2,3-Di(pyridin-2-yl)benzo[g]quinoxaline

“…The fluorescence lifetimes for dpb, 1-Cl, 2-Br, and 3-I were measured under both aerated and deaerated conditions and are listed in Table 2 complexes [where NN = 1,10-phenanthrolines (phen) with various methyl substitution patterns or a dihydrophenanthroline-based ligand] are also greater than those reported for the free ligands, although only qualitative comparisons can be made to dpb and the [Zn(dpb)X 2 ] complexes in this study because of differences in the photophysical properties of dpb and phen or experimental conditions. 105,110 Deaeration of the samples leads to a 12−70% increase in the fluorescence lifetimes of dpb and the [Zn(dpb)X 2 ] complexes, indicating significant quenching of the singlet excited states by dissolved O 2 in solution. The bimolecular quenching constants for dissolved O 2 with singlet excited states (k Q S ) were calculated to be on the order of ∼4 × 10 9 M −1 s −1 for the three [Zn(dpb)X 2 ] complexes, while k Q S for dpb appears to be diffusion-controlled in CH 3 CN at 1.38 × 10 10 M −1 s −1 .…”