Hydrothermal Synthesis, Structure, and Optical Properties of Two Nanosized Ln 26 @CO 3 (Ln=Dy and Tb) Cluster‐Based Lanthanide–Transition‐Metal–Organic Frameworks (Ln MOFs)

Two Ln 26 @CO 3 (Ln=Dy and Tb) cluster‐based lanthanide–transition‐metal–organic frameworks (Ln MOFs) formulated as [Dy 26 Cu 3 (Nic) 24 (CH 3 COO) 8 (CO 3 ) 11 (OH) 26 (H 2 O) 14 ]Cl ⋅ 3 H 2 O ( 1 ; HNic=nicotinic acid) and [Tb 26 NaAg 3 (Nic) 27 (CH 3 COO) 6 (CO 3 ) 11 (OH) 26 Cl(H 2 O) 15 ] ⋅ 7.5 H 2 O ( 2 ) have been successfully synthesized by hydrothermal methods and characterized by IR, thermogravimetric analysis (TGA), elemental analysis, and single X‐ray diffraction. Compound 1 crystallizes in the monoclinic space group Cc with a =35.775(12) Å, b =33.346(11) Å, c =24.424(8) Å, β =93.993(5)°, V =29065(16) Å 3 , whereas 2 crystallizes in the triclinic space group P $\bar 1$ with a =20.4929(19) Å, b =24.671(2) Å, c =29.727(3) Å, α =81.9990(10)°, β =88.0830(10)°, γ =89.9940(10)°, V =14875(2) Å 3 . Structural analysis indicates the framework of 1 is a 3D perovskite‐like structure constructed out of CO 3 @Dy 26 building units and Cu + centers by means of nicotinic acid ligand bridging. In 2 , however, nanosized CO 3 @Tb 26 units and [Ag 3 Cl] 2+ centers are connected by Nic − bridges to give rise to a 2D structure. It is worth mentioning that this kind of 4d–4f cluster‐based MOF is quite rare as most of the reported analogous compounds are 3d–4f ones. Additionally, the solid‐state emission spectra of pure compound 2 at room temperature suggest an efficient energy transfer from the ligand Nic − to Tb 3+ ions, which we called the “antenna effect”. Compound 2 shows a good two‐photon absorption (TPA) with a TPA coefficient of 0.06947 cm GM −1 (1 GM=10 −50  cm 4  s photon −1 ), which indicates that compound 2 might be a good choice for third‐order nonlinear optical materials.