The synthesis, structure and magnetothermal properties of three new lanthanide 1D polymeric complexes, {[Ln₂Ba(α-fur)₈(H₂O)₄]}_n for Ln = Nd (1), Er (2) and {[Ho₂Ba(α-fur)₈(H₂O)₄]⋅2H₂O}_n (3), based on carboxylic α-fur = C₄H₃OCOO ligands is reported. The α-furoate ligands consolidate zigzag chains formed by Ln₂ dimers separated by Ba ions. Ab initio calculations, in combination with the fit of experimental static magnetization and heat capacity, predict the magnetic ground state, energy levels and magnetic interactions in these heteronuclear nanomagnets. Nd₂Ba (1) presents two different coordination sites for Nd, with an orthorhombic magnetic ground state. Nd ions are coupled along the chain through a weak antiferromagnetic (AF) interaction J″/k_B = −0.08 K. Er(III) ions in Er₂Ba (2) present a highly axial ground state, forming magnetic dimers with an interaction of J′/k_B = −8.6 K, while interdimer coupling along the chain is J″/k_B = −0.28 K. The Ho₂Ba (3) complex consists of a highly anisotropic quasi-doublet with a Δ_Ho/k_B = 0.7 K gap. Non-Kramers Ho ions form magnetic dimers within the Ho₂Ba cluster, coupled by an AF intradimer interaction J′/k_B = −2.5 K. The three complexes exhibit in-field slow relaxation of the magnetization: 1 relaxes through an Orbach process at high temperatures [U_eff/k_B = 60(1) K] evolving to quantum tunneling below 3 K [τ_QT = 0.05(1) s]; 2 exhibits a rapid Orbach-like process [τ₀ = 8(6)⋅10^-8 s and U_eff/k_B = 10(2) K] and 3 shows a direct process [τ = 0.4(1) s].