Manipulating the crystal packing of pyDTDA radical ligand coordination complexes with Mn(ii) and Ni(ii)

Abstract

The synthesis of 4'-CN, 5'-CN and 5'-Br substituted pyDTDA neutral radical bidentate ligands is reported (pyDTDA = 4-(2'-pyridyl)-1,2,3,5-dithiadiazolyl). The Ni(hfac)(2) and Mn(hfac)(2) coordination complexes of both cyano substituted ligands, and the Mn(hfac)(2) coordination complex of the bromo substituted ligand, have been prepared and the crystal packing of these is compared (hfac = 1,1,1,5,5,5-hexafluoroacetylacetonato-). Unlike the previously reported Mn(hfac)(2)(pyDTDA), the Mn(hfac)(2)(4'-CN-pyDTDA) complex does not form dimers in the solid-state making it possible to measure the magnetic coupling between the unpaired electrons on the coordinated Mn(ii) ion and the unpaired electron on the radical ligand by SQUID magnetometry; J/k(B) = -74(1) K, using H = -2J{S(Mn).S(Rad)} and g(av.) = 2.01.

Metal-radical coordination complexes of thiazyl and selenazyl ligands

“…With these points in mind, it was initially postulated that the rigidity of the octahedral coordination environment, and resulting steric contributions, played a primary role in the crystal packing and lack of dimerization for M(hfac) 2 (pyDTDA) where M = Fe II , Co II , and Ni II , whereas distortions in the coordination geometry for M = Mn II and Cu II decreased the steric contribution enabling the formation of pancake bonds. In order to probe this postulate and attempt to manipulate the crystal packing of the DTDA-metal complexes through electrostatic contacts, Mn II and Ni II complexes of the 4′ and 5′cyanopyDTDA ligands, and the Mn II complex of 5′ bromopyDTDA where prepared [53]. The results indicate that the steric contribution from the hfac ligand field is not necessarily the major factor in the (non)formation of pancake bonds in the solid state.…”

“…The pyridyl and pyrimidyl heterocycles can be decorated with groups such as halides and nitriles in order to promote electrostatic contacts in the solid state and manipulate the crystal packing of the complexes. The 4′ and 5′cyanopyDTDA and the 5′bromopyDTDA ligands, and some of their transition metal complexes, have been reported [53].…”

Ambivalent binding between a radical-based pincer ligand and iron

“…35,36 Although dimerization occurs, stabilization of the radical may be accomplished through metal coordination, as has been shown to work with other radical based ligand systems. 37,38 The coordinating ability of Py 2 TTA • with redox active metal centres was, therefore, investigated. To that end, a solution of FeCl 2 in degassed MeCN was layered over a solution of Py 2 TTA • in degassed chloroform (CHCl 3 ) under an inert environment.…”

Elucidating the 2D Magnetic Topology of the ‘Metal–Radical’ TTTA⋅Cu(hfac)2 System

“…The [M(hfac) 2 ] ⋅ [organic radical] units usually dimerize into a two‐M(hfac) 2 and two‐radical spin array, which are AFM or show no magnetic signal 8d. 12, 13a,b Other coordination complexes range from mononuclear,5a, 13c dinuclear,8d, 13c,d and trinuclear8b,d clusters to ring8d topologies. Among them only the o ‐pyDTDA ⋅ Co(hfac) 2 5a, 13c and 4‐PC ⋅ Cu(hfac) 2 15 mononuclear and the imino ⋅ Cu(hfac) 2 8d trinuclear complexes show FM interactions; all the others are AFM‐coupled.…”