Self-condensation of bifunctional 8-aminoquinoline-2-carbaldehyde templated by dysprosium(III) ions followed by the replacement of axial ligands with triphenylsilanol in the presence of Et₃N produced two belt macrocycle complexes, [Dy(L1^N6)(Ph₃SiO)₂][ClO₄] (1) and [Dy(L1^N6)(Ph₃SiO)₂][OTf] (2) (L1^N6 = 2,5,8-triaza-1(8,2),4,7(2,8)-triquinolinacyclononaphane-2,5,8-triene). For comparison, other kinds of belt macrocycle complexes [Dy(RRRR-L2^N6)(Ph₃SiO)₂][(3-Br-C₆H₄)B(C₆H₅)₃] (3R), [Dy(SSSS-L2^N6)(Ph₃SiO)₂][(3-Br-C₆H₄)B(C₆H₅)₃] (3S), [Dy(RRRR-L2^N6)(Ph₃SiO)₂][(4-Br-C₆H₄)B(C₆H₅)₃] (4R) and [Dy(SSSS-L2^N6)(Ph₃SiO)₂][(4-Br-C₆H₄)B(C₆H₅)₃] (4S) (L2^N6 = (2E,5E,8E,11E)-3,5,9,11-tetraaza-1,7(2,6)-dipyridina-4,10(1,2)-dicyclohexanacyclododecaphane-2,5,8,11-tetraene) were also prepared using the same procedure except that the equatorial macrocycle was built from a [2 + 2]-condensation of cyclohexane-1,2-diamine and pyridine-2,6-dicarbaldehyde. These structurally similar complexes have almost identical axial Dy–O distances but distinguishable equatorial Dy–N distances, i.e. longer Dy–N distances were observed in 1 and 2, suggesting a weaker equatorial crystal field. Magnetism measurements reveal a typical zero-field single-molecule magnet (SMM) behavior with the effective energy barriers (U_eff) up to 1732(43) K, 1680(9) K, 1363(22) K/1415(24) K and 1369(34) K/1434(29) K for 1, 2, 3R/3S and 4R/4S, respectively. The experimental results are supported by ab initio calculations, which exhibit relaxation of the magnetization via higher excited states in 1 and 2 as the consequence of a weaker equatorial crystal field and a less distorted coordination geometry, which efficiently hampers the transverse components of magnetization. This work unequivocally evidenced the dominance of L1^N6 over L2^N6 in weakening the transverse crystal field, providing a new route to construct high-performance air-stable lanthanide SMMs.

Mononuclear [Dy(L¹ _R/S)(4-Me-PhO)₂](BPh₄) (1R/1S) and dinuclear [Dy₂(L² _R/S)₂(4-Me-PhO)₂(OH)₂](BPh₄)₂ (2R/2S) chiral dysprosium(III) complexes were synthesized using equatorial hexaazamacrocycle and p-cresol axial ligands. Structural and magnetic analyses revealed that 1R/1S are high-performance single-molecule magnets due to their nearly perfect D_6h local symmetry. Hydroxo-bridged dinuclear species 2R/2S with nine-coordinate hula-hoop geometry possess strong intramolecular ferromagnetic interactions as proven by the electrostatic model, suppressing quantum tunnelling of magnetization (QTM) to some extent.

A five-coordinate mononuclear Dy( iii ) complex was constructed using a super bulky Schiff-base ligand, which shows a strong block of magnetization with a U _eff of ca. 1200 cm ⁻¹ and a T _B of 20 K.

Air-stable chiral Dy(iii) SMMs with terminal fluoride ligands and supported by a bulky equatorial macrocycle were synthesized.

A pair of double-decker Dy( iii ) macrocyclic enantiomers featuring sole fluoride axial ligands were designed and synthesized, which exhibit strong intramolecular ferromagnetic coupling and two-step relaxation of magnetization.

Boron-assisted highly symmetric lanthanide (Ln) macrocycles, (η²-catechol-μ-catecholborate)₃Ln(Ph₃PO)₂·xC₇H₈ (Ln = Dy, x = 0, Dy-B-Ph₃PO; Ln = Yb, x = 1, Yb-B-Ph₃PO) have been achieved by a one-pot reaction of Ln[N(TMS)₂]₃ (TMS = –SiMe₃) with excess catecholborane (HBCat) in the presence of Ph₃PO. Both macrocycles exhibit high brightness and long lifetimes benefitting from the combination of the rigid molecular backbone and the diminishing detrimental high energy X–H (X = C, N and O) vibrations. In particular, Dy-B-Ph₃PO exhibited the longest ⁴F_9/2 lifetime beyond 200 μs to date. When (4-(anthracen-9-yl)phenyl)diphenylphosphine oxide (AnPh₃PO) was used as the antenna ligand, a highly luminescent NIR bioprobe, Yb-B-AnPh₃PO, showing no apparent cell toxicity and high quality in vitro imaging, was obtained. Furthermore, the synthetic versatility of this system permits additional investigations of multifunctional Ln molecular materials in the future.