A Dinuclear (μ‐Carboxylato)manganese(II) Complex Derived from a Macrocyclic Ligand: A Structural Model for Active Sites in Natural Systems

Abstract

Ox! hrn/iporpliyi-iii 3. 3 i-ip).rranediciirhoxylic acid (4) (200 mg) was stirred with trifluoroacetic acid (2 m L ) under an atmosphere of nitrogen for 10 min. Dicliloroiiieth,iii~ (38 mLJ was added. followed immediately by 5-formylsalicylaldeh y k ( 6 6 iiig), ;itid the mixture wa\ stirred under nitrogen for a further 2 h. The iiiixturc ~i i j iieiitidized by the dropwise addition of triethylainine, DDQ (102 ing) wiis .iddcd, ,itid tlic rcsultin_e solution was stirred for a n additional 1 h The mixture wiij iv,ishcd w t l i \~. i t~i -and chromatographed on alumina (Grade 3) hy eluting first with dich1ororneth;ine and then with chloroform. A deep green fraction was collectilli/ed from chloroform,inethaiioI to give the porphyrm analog I \ hright purple microneedles Selected physical and spectroscopic data f;)i 3: ni p 261 262 C (decomp.): U V , V i s (CH,CIJ: imi, ( l g~) = 426 (5.05).

Polynuclear MnII Complexes with Chloroacetate Bridge − Syntheses, Structure, and Magnetic Properties

“…The three compounds studied here show weak Mn ··· Mn interactions, so even at low temperatures several spin states may be populated. This may lead to many possible transitions, and thus to a complicated EPR spectrum 30. At room temperature all the complexes show a broad signal centered at g ≈︁ 2.…”

“…There are also some dinuclear compounds which only have carboxylate bridges, e.g. three,9,15−18 two,19−29 or one 30,31…”

Dinuclear copper-(I) and -(II) complexes derived from a diprotonated Schiff-base cryptand

“…The N-donor atoms of the pendant arms in the dicopper() complex 4 approach the metal atoms from the same side of the macrocyclic ring ('cis') consistent with the clipping out of one bridge from the cryptate precursor (Scheme 2). This process has also been demonstrated in a dimanganese() complex, 14 [Mn 2 L 6 (O 2 CMe)][BF 4 ] 3 , and may be contrasted with the approach of the methoxyethyl pendant arms from opposing side ('trans') found in [Cu 2 L 1 ]-[ClO 4 ] 4 formed by transmetallation of the mononuclear barium precursor complex 1. 2 Furthermore the co-ordination geometries at the metal atoms differ; those at the copper atoms in the [Cu 2 L 1 ] 4+ cation are very close to square pyramidal (the index of trigonality τ being 0.075 based on the pendant-arm donor atom being the axial donor atom, Scheme 3), whereas each copper atom in 4 is five-co-ordinate with a distorted trigonal-bipyramidal geometry (τ lies between 0.33 and 0.47).…”

“…Such behaviour has been noted in the reactivity of an isophthaldehyde-derived cryptand with copper() 13 and in the reaction of L 2 with manganese(). 14 Recrystallisation of complex for X-ray crystallography. The results of X-ray analysis confirm the ring opening of the Schiff-base cryptand, caused by scission of one pyridinyl diimine unit, has occurred such that the dicopper() moiety is held inside a cleft.…”

Dinuclear silver(I) complexes of bibracchial tetraimine Schiff base macrocycles derived from pyrrole-2,5-dicarbaldehyde

“…Mono-or homodi-nuclear metal-containing molecular clefts can be synthesized from the cyclocondensation of functionalised triamines with 2,6-diacetylpyridine, pyridine-2,6dicarbaldehyde, thiophene-2,5-dicarbaldehyde and furan-2,5dicarbaldehyde in the presence of appropriate metal templates such as barium and silver(). [1][2][3][4][5][6][7][8][9][10][11][12][13] The clefts are derived from bibracchial tetraimine Schiff base macrocycles such as L 1 and L 2 and have been used, via transmetallation reactions, to complex copper() and manganese(). The incorporation of a range of functionalised triamines has provided the conformational flexibility to vary the homodinuclear intermetallic separation from ca.…”