2 research outputs found
Conglomerate, Racemate, and Achiral Crystals of Polymetallic Europium(III) Compounds of Bis- or Tris-β-diketonate Ligands and Circularly Polarized Luminescence Study
This work reports
(a) conglomerate and racemic crystal structures
of [(Δ,Δ,Δ,Δ,Δ,Δ)- or/and (Λ,Λ,Λ,Λ,Λ,Λ)-EuIII6(TTP)8(OH2)6Na4]n coordination polymers,
(b) racemic crystal structures of (Δ,Δ,Δ,Δ)-/(Λ,Λ,Λ,Λ)-EuIII4(TTP)4(bipy)4(MEK)2(OH2)2 tetrahedral clusters, and (c)
the achiral crystal structure of the [EuIII2(BTP)4(OH2)2Na2]n coordination polymer (where BTP = dianionic
bis-β-diketonate, TTP = trianionic tris-β-diketonate, and bipy = 2,2′-bipyridine). The screw coordination
arrangement of the TTP ligand has led to the formation of homoconfigurational
racemic EuIII products. The conglomerate crystallization
of [EuIII6(TTP)8(OH2)6Na4]n appears to be
caused by the presence of the sodium, Na+ counterions,
and interactions between oxygen atoms and the trifluoromethyl unit
of the TTP ligand and Na+ ions. All the EuIII compounds exhibit characteristic red luminescence (5D0 → 7FJ, J =
0–4) in solution or in the solid crystalline state. Circularly
polarized luminescence (CPL) was observed in the chiral EuIII6(TTP)8(OH2)6Na4]n species, displaying a |glum| value in the range of 0.15 to 0.68 at the 5D0 → 7F1 emission band. Subtle
changes of the [EuIII6(TTP)8(OH2)6Na4]n structure
which may be due to selection of twinned crystals or crystals that
do not correspond to a perfect spontaneous resolution, are considered
to be responsible for the variation in the observed CPL values
Excited State Engineering in Ag<sub>29</sub> Nanocluster through Peripheral Modification with Silver(I) Complexes for Bright Near-Infrared Photoluminescence
The optical property of an ionic metal nanocluster (NC)
is affected
by the ionic interaction with counter ions. Here, we report that the
modification of trianionic [Ag29(BDT)12(TPP)4]3– NC (BDT: 1.3-benzenedithiol; TPP: triphenylphosphine)
with silver(I) complexes led to the intense photoluminescence (PL)
in the near-infrared (NIR) region. The binding of silver(I) complexes
to the peripheral region of Ag29 NC is confirmed by the
single-crystal X-ray diffraction (SCXRD) measurement, which is further
supported by electrospray ionization mass spectrometry (ESI-MS) and
nuclear magnetic resonance (NMR) spectroscopy. The change of excited-state
dynamics by the binding of silver(I) complexes is discussed based
on the results of a transient absorption study as well as temperature-dependent
PL spectra and PL lifetime measurements. The modification of Ag29 NCs with cationic silver(I) complexes is considered to give
rise to a triplet excited state responsible for the intense NIR PL.
These findings also afford important insights into the origin of the
PL mechanism as well as the possible light-driven motion in Ag29-based NCs