Counterfeit goods represent a major problem to companies, governments, and customers, affecting the global economy. In order to protect the authenticity of products and documents, optical anti‐counterfeit technologies have widely been employed via the use of discrete molecular species, extended metal–organic frameworks (MOFs), and nanoparticles. Herein, for the first time we demonstrate the potential use of molecular cluster‐aggregates (MCA) as optical barcodes via composition and energy transfer control. The tuneable optical properties for the [Ln20(chp)30(CO3)12(NO3)6(H2O)6], where chp−=deprotonated 6‐chloro‐2‐pyridinol, allow the fine control of the emission colour output, resulting in high‐security level optical labelling with a precise read‐out. Moreover, a unique tri‐doped composition of GdIII, TbIII, and EuIII led to MCAs with white‐light emission. The presented methodology is a unique approach to probe the effect of composition control on the luminescent properties of nanosized molecular material.

Inducing magnetic coupling between 4f elements is an ongoing challenge.T oo vercome this formidable difficulty, we incorporate highly delocalized tetrazinyl radicals,w hich strongly couple with f-blockm etallocenes to form discrete tetranuclear complexes.S ynthesis,s tructure,a nd magnetic properties of two tetranuclear [(Cp* 2 Ln) 4 (tzC) 4 ]•3(C 6 H 6 ) (Cp* = pentamethylcyclopentadienyl;t z = 1,2,4,5-tetrazine; Ln = Dy,G d) complexes are reported. An in-depth examination of their magnetic properties through magnetic susceptibility measurements as well as computational studies support ah ighly sought-after radical-induced "giant-spin" model. Strong exchange interactions between the Ln III ions and tzC radicals lead to as trong magnet-like behaviour in this molecular magnet with alarge coercive field of 30 kOe.

Amidine-based ligand frameworks were employed to isolate a series of mononuclear lanthanide complexes. The employed N-2-pyridyl­imidoyl-2-pyridyl­amidine (Py2ImAm) undergoes metal-assisted hydrolysis yielding the ligand 2-amidino­pyridine (PyAm), which coordinates to the lanthanide ions affording [Ln­(acac)3(PyAm)], where Ln = Eu­(III) (1), Gd­(III) (2), Tb­(III) (3), Dy­(III) (4) along with the Y­(III) analogue (5). The Eu­(III), Tb­(III), and Dy­(III) congeners exhibit characteristic emissions of red, green, and yellow light, respectively, with emission quantum yields of 3, 65, and 8%, respectively. Due to changes in the thermal population of the Stark sublevels, the Tb­(III) and Dy­(III) complexes can be used as efficient optical thermometers with maximum relative sensitivities of 1.57 and 2.03% K–1 for 3 and 4, respectively. These results demonstrate the viability of PyAm as an antenna for the sensitization of lanthanide ions.

Trivalent lanthanide ions (Ln 3+ ) are used to prepare a plethora of coordination compounds; metal-organic frameworks (MOFs) being amongst the most sought-after in recent years. The porosity of Ln-MOFs is often complemented by the luminescence imparted by the metal centers, making them attractive multifunctional materials. Here, we report a class of 3D MOFs obtained from solvothermal reaction between 2,6-naphtalenedicarboxylic acid (H 2 NDC) and lanthanide chlorides yielding three types of compounds depending on the chosen lanthanide: [LnCl(NDC)(DMF)] for Ln 3+ = La 3+ , Ce 3+ , Pr 3+ , Nd 3+ , Sm 3+ (type 1), [Eu(NDC) 1.5 (DMF)]•0.5DMF (type 2), and [Ln 2 (NDC) 3 (DMF) 2 ] (type 3) for Ln 3+ = Tb 3+ , Dy 3+ , Y 3+ , Er 3+ , Yb 3+ . Photoluminescent properties of selected phases were explored at room temperature. The luminescence thermometry capability of Yb 3+ -doped Nd-MOF was fully investigated in the 15-300 K temperature range under 365 and 808 nm excitation. To describe the optical behavior of the isolated MOFs, we introduce the total energy transfer balance model. Therein, the sum of energy transfer rates is considered along with its dependence upon the temperature: sign, magnitude, and variation of this parameter, permitting to afford a thorough interpretation of the observed behavior of the luminescent species of all materials presented here. The combination of novel theoretical and experimental studies presented herein to describe energy transfer processes in luminescent materials can pave the way towards the design of MOF-based chemical and physical sensors working in an optical range of interest for biomedical applications.

The reactions of various copper(ii) sources with 2-acetylpyridine, (py)(me)CO, and 2-benzoylpyridine, (py)(ph)CO, under strongly basic conditions have been studied and novel ligand transformations have been discovered. Reaction of Cu(ClO4)2·6H2O and (py)(me)CO in the presence of NBu4(n)OMe (1 : 1 : 1) in CHCl3 gave a mixture of [Cu2Cl2(HLA)2](ClO4)2 (1) and [Cu2Cl2(LB)2(ClO4)2] (2), where HLA is 3-hydroxy-1,3-di(pyridin-2-yl)-butane-1-one and LB is the zwitterionic-type ligand 3-hydroxy-1-methyl-3-(pyridin-2-yl)-3H-indolizin-4-ium. The ligand HLA is formed through an aldol reaction-type mechanism, while the formation of LB takes place via an intramolecular nucleophilic attack of the remote 2-pyridyl nitrogen atom on the positive carbonyl carbon of HLA, after the transformation of the latter through deprotonation and dehydration. The Cu(II) ions in 1 are bridged by two 2.1111 HLA ligands resulting in a long Cu(II)Cu(II) distance (5.338 Å); the metal ions in 2 are triply bridged by the alkoxide oxygen atoms of the two 2.21 LB ligands and one 2.1100 perchlorato group. The absence of α-hydrogens in (py)(ph)CO leads the reactivity of this ligand in the presence of Cu(II) to different pathways. The Cu(ClO4)2·6H2O/(py)(ph)CO/NBu4(n)OMe reaction mixture in MeOH/H2O (25 : 1 v/v) gave the dinuclear cationic complex [Cu2{(py)(ph)CO}2(LC)2](ClO4)2 (3), where LC(-) is the anion of (methoxy)(phenyl)(pyridin-2-yl)methanol formed in situ via the nucleophilic addition of MeO(-) to the carbonyl carbon of (py)(ph)CO upon Cu(II) coordination. The Cu(II) ions in the cation are doubly bridged by the deprotonated oxygen atoms of the two LC(-) ligands. Replacement of Cu(ClO4)2·6H2O with Cu(NO3)2·3H2O and NBu4(n)OMe with NMe4OH and the decrease of the H2O concentration in the above reaction system yielded the tetranuclear coordination cluster [Cu4(OMe)2(NO3)4{(py)(ph)CO}2(LC)2] (4). The Cu(II) centres in this complex define a parallelogram. Two parallel sides of the parallelogram are each supported by deprotonated oxygen atoms belonging to a 2.21 LC(-) ligand and a 2.2 MeO(-) group. The metal ions that define each of the other two sides are singly bridged by an oxygen atom of a 2.210 nitrato group. No bridging exists between the Cu(II) ions that define the two diagonals of the parallelogram. Replacement of MeOH with EtOH in the reaction system that gave 4 resulted in the dinuclear complex [Cu2(NO3)2(LD)2)(EtOH)] (5), LD(-) being the anion of (ethoxy)(phenyl)(pyridin-2-yl)methanol. The Cu(II) ions are doubly bridged by the alkoxide oxygen atoms of the two 2.21 LD(-) ligands. The 1 : 1 : 1 Cu(NO3)2·3H2O/(py)(ph)CO/NMe4OH reaction system in CH3NO2 gave the dinuclear complex [Cu2(NO3)2(LE)2] (6), where LE(-) is the anion of 2-nitro-1-phenyl-1-(pyridin-2-yl)ethanol. The OH(-) ion abstracts one of the methyl hydrogens of CH3NO2, and once the carbanion (-):CH2NO2 is formed it attacks the positive (δ+) carbonyl carbon of (py)(ph)CO; as the carbanion forms the new C-C bond, the π electrons of the carbonyl group of the original ligand are transfer...