A new series of potentially hexadentate ligands derived from 2,2′-bipyridine

1H NMR spectroscopic elucidation in solution of the kinetics and thermodynamics of spin crossover for an exceptionally robust Fe2+ complex

“…Complexes of this type were reported before by Constable, 11 Kol 12 and Blackman. 13,14 However, all of those Fe 2+ -complexes were described as LS Fe 2+ complexes. Herein, we wish to report topologically related complexes that employ an aliphatic 1,2-diaminocyclohexane (4) fragment as the bridge.…”

Factors influencing mononuclear versus multinuclear coordination in a series of potentially hexadentate acyclic N6 ligands: the roles of flexibility and chelate ring size

“…The synthesis of the hydrochloride salts of the bmet and bmpp ligands has been previously reported. 17 The free base bmet and bmpp ligands were obtained by the reductive amination of 2,2¢bipyridine-6-carbaldehyde with the appropriate diamine, using an analogous method to that of Baird and coworkers in the synthesis of the ligand hydrochloride salts. The new ligands bmbu, bmpt and bmot were prepared by similar methods, with bmbu isolated as the hydrochloride salt, bmot as the free base, and bmpt as both.…”

“…17 reduces the number of possible geometric isomers to one. 17 The 6-membered aliphatic ring in [Co(bmpp)] 3+ and the 7-membered aliphatic ring in [Co(bmbu)] 3+ (see below) also display surprising rigidity, as evidenced by the observation of three, and four, 2proton multiplets, respectively, in the methylene region. These numbers of signals are consistent with geminal coupling between the aliphatic protons, and fewer signals would be observed if the chelate ring displayed significant mobility.…”

“…16 Recently we designed a series of acyclic ligands containing bipyridine units connected to an aliphatic diamine, which can be viewed as hybrids of those discussed above, and which therefore can potentially bind so as to give either mononuclear complexes, or homoleptic multinuclear complexes. 17 As can be seen from the structures of these outlined in Fig. 1, they differ only in the length of the alkyl chain in the aliphatic diamine.…”

Same head, different scaffold: a plethora of structural motifs assembled from silver(i) and ditopic 2,2′-bipyridine ligands

“…[8][9][10][11][12][13][14] Blackman has recently described the condensation of 2,2 0bipyridine-6-carbaldehyde with ethane-1,2-diamine, propane-1,2-diamine and hexane-1,6-diamine followed by borohydride reduction to give a family of hexadentate ligands with saturated spacers between the two bpy domains (bpy ¼ 2,2 0 -bipyridine). 15 The backbone of the shortest of these ligands is flexible enough to permit the ligand to bind a single cobalt(II) ion within an N 6donor set. Significantly, we have noted that reduction of (R,R)-2 increases the flexibility of the ligand, resulting in a preference for a mononuclear complex when it binds copper(II), zinc(II) or iron(II) in contrast to the [2 + 2] helicates that assemble when (R,R)-2 reacts with zinc(II) or silver(I) or when (S,S)-2 binds iron(II).…”