title: Construction of Identical [2 + 2] Schiff-Base Macrocyclic Ligands by Ln(III) and Zn(II) Template Ions Including Efficient Yb(III) Near-Infrared Sensitizers.
abstract: Identical 34-membered [2 + 2] pendent-armed Schiff-base macrocyclic ligands (H4La and H4Lb) can be constructed via the condensation reactions between rigid o-phenylenediamine and extended dialdehydes (H2hpdd/H2pdd) in the presence of either Ln(III) or Zn(II) template with remarkable distinction on the ion radii and charge. X-ray single-crystal diffraction analyses reveal the formation of mononuclear Ln(III) complexes (1-4 and 7) and dinuclear Zn(II) complexes (5 and 6). It is noted that Ln(III) macrocyclic complexes have eight-coordinate sandwich-like mononuclear structures fully surrounded by flexible and large-sized macrocyclic ligands. Photophysical studies have demonstrated that both H4La and H4Lb can serve as effective sensitizers for the Yb(III) ion (2 and 7) exhibiting near-infrared emission at 974 nm with high quantum yields in solution (C2H5OH and CH3OH, ∼1%). Moreover, the quantum yields of two Yb(III) complexes 2 and 7 could be increased ∼15% in CH3OH under weak alkaline condition (pH = 8-9), while no significant changes are observed in C2H5OH by contrast. We think the unique sandwich-like macrocyclic structures of Yb(III) complexes 2 and 7 play important roles in simultaneously guaranteeing the effective match of the energy levels of Yb(III) centers as well as shielding from the solvent molecules and counterions.
authors.affiliation: State Key Laboratory of Coordination Chemistry, Nanjing National Laboratory of Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, People's Republic of China.
authors.forename: Kun
authors.initials: K
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Coordination Chemistry, Nanjing National Laboratory of Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, People's Republic of China.
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Coordination Chemistry, Nanjing National Laboratory of Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, People's Republic of China.
authors.forename: Song
authors.initials: S
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Coordination Chemistry, Nanjing National Laboratory of Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, People's Republic of China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Hu
authors.affiliation: State Key Laboratory of Coordination Chemistry, Nanjing National Laboratory of Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, People's Republic of China.
authors.forename: Youxuan
authors.initials: Y
authors.lastname: Zheng
authors.affiliation: State Key Laboratory of Coordination Chemistry, Nanjing National Laboratory of Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Huang
mesh_terms: D018360:Crystallography, X-Ray; D028581:Lanthanoid Series Elements / Q000138:chemical synthesis / Q000737:chemistry*; D008024:Ligands; D049449:Luminescence; D049408:Luminescent Agents / Q000138:chemical synthesis / Q000737:chemistry*; D047028:Macrocyclic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D008958:Models, Molecular; D012545:Schiff Bases / Q000138:chemical synthesis / Q000737:chemistry*; D015018:Ytterbium / Q000737:chemistry; D015032:Zinc / Q000737:chemistry*
chemical_list: D028581:Lanthanoid Series Elements; D008024:Ligands; D049408:Luminescent Agents; D047028:Macrocyclic Compounds; D012545:Schiff Bases; D015032:Zinc; D015018:Ytterbium