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 (H(2)hpdd/H(2)pdd) 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, similar to 1%). Moreover, the quantum yields of two Yb-III complexes 2 and 7 could be increased similar to 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.