Hydrothermal synthesis, structure, and properties of two new nanosized Ln ₂₆ (Ln=Ho, Er) clusters

Two new compounds, [Ho ₂₆(IN) ₂₈(CH ₃COO) ₄(CO ₃) ₁₀(OH) ₂₆(H ₂O) ₁₈]20H ₂O (1) (HIN=isonicotinic acid) and [Er ₂₆(IN) ₂₉(CH ₃COO) ₃(CO ₃) ₁₀(OH) ₂₆(H ₂O) ₁₉] 26H ₂O (2), employing the building unit of CO ₃@Ln ₂₆ have been synthesized hydrothermally. Compound 1 crystallizes in the triclinic space group with a=21.043(4)Å, b=21.128(5)Å, c=35.140(8)Å, α=85.838(3)°, β=74.909(3)°, γ=85.414(3)°, V=15,014(6)Å ³, Z=2; 2 crystallizes in triclinic with a=20.9968(15)Å, b=21.1260(15)Å, c=35.125(3)Å, α=85.9530(10)°, β=74.7590(10)°, γ=85.5020(10)°, V=14,966.3(18)Å ³, Z=2. In the structures of both compounds, the isonicotinate (IN) is the main ligand while CH ₃COO ^- functions as the second ligand to stabilize the Ln ₂₆ cluster; plays a very important role in the formation of the spherical Ln ₂₆ cluster. The two compounds are isostructural and have been characterized by single-crystal X-ray diffraction, IR absorption spectroscopy, thermogravimetric analysis, ultraviolet excitation, and emission spectrum.