New NIR-emissive tetranuclear Er(iii) complexes with 4-hydroxo-2,1,3-benzothiadiazolate and dibenzoylmethanide ligands: synthesis and characterization

Abstract

New tetranuclear heteroleptic complexes [Er4(dbm)6(O-btd)4(OH)2] (1) and [Er4(dbm)4(O-btd)6(OH)2] (2) (O-btd = 4-hydroxo-2,1,3-benzothiadiazolate and dbm = dibenzoylmethanide) and their solvates with toluene, THF and CH2Cl2 were prepared using two synthetic approaches. The structures of the products were confirmed by single-crystal X-ray diffraction. Magnetic properties of 1 and 2 are in good agreement with X-ray data. The effective magnetic moment (μeff) values at 300 K for 1 and 2 corresponds to a system of 4 non-interacting Er(III) ions in the ground state 4J15/2 with g = 6/5. At ambient temperature and upon excitation with λexc = 450 nm, complexes 1 and 2 exhibit luminescence at 1530 nm, i.e. in the near infra-red (NIR) region. The luminescence intensity grows with increasing the number of the (O-btd)− ligands in the complexes. This observation suggests (O-btd)− as a new efficient antenna ligand for the lanthanide-based NIR luminescence.

Chalcogen Bonding “2S–2N Squares” versus Competing Interactions: Exploring the Recognition Properties of Sulfur

“…An analysis of the correlation between CB ave distance and the associated angles q, f,a nd F for each structure shows that those with close contacts (CB ave van der Waals radii sum N + S = 3.35 ) [78] have angular ranges of q ave = 67.7-89.78 (mean 74.08), f ave = 0-36.38 (mean 1.78)a nd F ave = 149.6-179.58 (mean 171.68). Every structure in this category contains ah ighly aligned square planar interaction, with angles approaching f% 08, q % 908,a nd F % 1808.T he shortest (2.89 ), [76] middle (3.39 ) [79] and longest (3.95 ) [77] CB ave distances,r espectively,i llustrate the marked diversity in 2S-2N square 2,1,3-benzothiadiazole dimer structures that fall within the 2.89-4.0 CB ave range ( Figure S10). The strikingly high prevalence of diverse structures (39) containing both sub-van der Waals S···Nc ontacts and highly aligneds quare planar interactions suggestst hat the square attraction out-competes the myriad of other substituent interactions during packing.…”

Rare‐Earth Metal Oxo/Hydroxo Clusters – Synthesis, Structures, and Applications

“…We and others have established the synthesis of pentanuclear lanthanide hydroxo clusters by treatment of the trichlorides of the smaller lanthanides [LnCl 3 ·(H 2 O) n ] (n = 6, 7) with dibenzoylmethane (Ph 2 acacH) in organic solvents in the presence of an organic base such as triethylamine or KOtBu. Another route to these compounds is by treatment of [Ln(Ph 2 acac) 3 10 ] (Ln = Y, [10] Nd, [49] Eu, [50][51][52][53] Tb, [52] Dy, [54] Ho, [53] Er, [49,55] Yb; [49] Scheme 3), in which the lanthanide atoms build up a square pyramidal scaffold by occupying its vertices (Figure 6), were obtained. In each of these structures, the square base face of the pyramid is capped by one μ 4 -oxygen atom, whereas its four triangular faces are capped by one μ 3 -oxygen moiety each.…”

“…[34] In a similar way the tetranuclear complexes [Er 4 (Ph 2 acac) 6 -(O-btd) 4 4 (O-btd) 6 (OH) 2 ] (O-btd = 4-hydroxy-2,1,3-benzothiadiazolate) were synthesized. [55] Obviously, the choice of the right co-ligand is crucial for obtaining the pentanuclear structural motif. We showed that amino acids are the ideal co-ligands to stabilize the pentanuclear lanthanide scaffold.…”

“…[37] Beside the usage of alkoxides as ligands, such pentanuclear cluster compounds with other ligands, such as dibenzoylmethane and functionalized versions of it, are also known. [10,[49][50][51][52][53][54][55] According to Evans et al, the reaction between europium metal and 2,6-diisopropylphenol in propan-2-ol leads to the formation of pentanuclear complex H 5 [Eu 5 O 5 (OC 6 H 3 iPr 2 -2,6) 6 -(NCCH 3 ) 8 ] after recrystallization from acetonitrile. [56] This mixedvalence compound features the known square pyramidal cluster core with four Eu II ions at the basal positions and one Eu III ion at the apex.…”

Electrochemical reduction, radical anions, and dehalogenation of fluorinated/chlorinated 2,1,3-benzothia/selenadiazoles

“…For these reasons, 2,1,3-benzothia/selenadiazoles found numerous applications as electron-acceptor or/and luminescent building blocks of real or potential molecular functional materials for electronics, optoelectronics and photovoltaics. 4,5,[13][14][15][16][17][18][19][20][21][22][23][24][25] Despite fluorinated (hetero) aromatics are promising for electronic and optoelectronic applications, 26,27 fluorinated 2,1,3-benzothia/selenadiazoles are less studied in this context. Hydrogen replacement by fluorine affects many properties of (hetero) aromatics including (hetero) aromaticity itself.…”