Impact of nuclearity and topology on the single molecule magnet behaviour of hexaazatrinaphtylene-based cobalt complexes

Abstract

A hexaazatrinaphtylene-based transition metal complex that exhibits single molecule magnet (SMM) behaviour is reported herein. Both monometallic (1) and bimetallic (2) CoII complexes with distorted octahedral geometries could be obtained through a straightforward change in synthetic conditions. Field induced SMM behaviour was exhibited by 1, with a D value of -60 cm-1 and Ueff = 17 K originating from the unquenched orbital angular momentum of the octahedral CoII (d7) centre. On the other hand, 2 exhibits weak antiferromagnetic interactions with a positive D value, thus preventing the observation of SMM behaviour. This investigation reveals the influence of both nuclearity and topology on the magnetic properties of HATN based complexes.

Acid Responsive Hydrogen-Bonded Organic Frameworks

“…Introducing nitrogen atoms into polycyclic aromatic hydrocarbons allows (1) fine-tuning of frontier orbital levels, lowering LUMO levels in many cases, (2) coordinating with metal cations, and (3) interacting with cationic species such as metal ions, proton, and other organic cations. After establishment of a facile synthetic route, HATN and its analogues have been widely applied for electron-transporting materials, ligands of novel metal complexes, receptor for cations, catalysts, single-molecular magnets, cathode of lithium batteries, and metal–organic frameworks, in addition for a mesogen of liquid crystals . More recently, HATN segments are used for constructing COFs applicable hydrogen storage, lithium battery, Pb­(II) cation scavenger, and catalyst .…”

Doublet-Singlet-Doublet Transition in a Single Organic Molecule Magnet On-Surface Constructed with up to 3 Aluminum Atoms

“…Going a step further in intramolecular spin frustration and ordering, a doubletsinglet-doublet magnetic transition is also observed in solution for only a few organometallic complexes when coordinating not two but three d electron transition-metal atoms. 9,10 We demonstrate here that this doublet-singlet-doublet transition can now be observed step-by-step by coordinating 1, 2, and 3 Al adatoms to a 1,8,9,16,17,24-hexaazatrianthracene (C 36 N 6 H 18 ; HATA) long aza-starphene molecule also on the Au(111) surface. Furthermore, the coordination of 3 Al adatoms to HATA on a surface is freezing its lateral surface vibrational mode.…”

“…Here, we went a step further, observing an on-surface doublet-singlet-doublet transition with no d electron transition metal atom involved. Such doublet-singlet-doublet transition is seldom observed in solution with organometallic transition metal complexes (see, for example, with hexaazatrinaphtynene (HAN)-based cobalt complexes , ) because of the structural flexibility of those complexes in solution that plays against spin ordering. , On-surface coordination chemistry is compensating this effect and gives access to other resonances as discussed below. With the d I /d V mapping around zero bias presented in Figure b, the spin-density distribution along the ligands can be unambiguously attributed to a Kondo-state.…”

A dinuclear Co(iii)/Co(ii) complex based on the H2pmide ligand showing field-induced SMM behaviour

“…3,16 However, of the several distorted octahedral Co(II) complexes found in the literature, only a few are stabilized with easy-axis anisotropy. [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] In this context, in our continuous research on Co(II) systems, we explored the reaction of the well-known pivalate Co(II) dinuclear reagent (Co 2 piv) 36 with the N-(2-pyridylmethyl) iminodiethanol (H 2 pmide) ligand. We have isolated a mixed valent dinuclear complex of formula [Co III Co II ( pmide) ( piv) 3 (H 2 O)] (1) with Co(II) in a distorted octahedral environment.…”

“…3,16 However, of the several distorted octahedral Co( ii ) complexes found in the literature, only a few are stabilized with easy-axis anisotropy. 17–35…”