The first amino acid bound manganese–calcium clusters: a {[MnIII3Ca]₂} methylalanine complex, and a [MnIII6Ca] trigonal prism

Abstract

An amino acid containing octanuclear heterometallic {[MnIII3Ca]2} cluster has been synthesized, alongside a structurally-related trigonal prismatic [MnIII6Ca]2+ cage.

Search for Structurally Resembled Mn/Ca Cubane Core of the Oxygen Evolving Complex of Photosystem II Yielded MnIV, MnIII3MnII and MnIII2CaII2Entities: Structure and Magnetism

“…Constantinos J Milios and his group also came up with Mn III 6 Ca 2 synthesized by utilizing an oxime‐based ligand [25] . Recently this group divaulged an amino acid (Methylalanine) containing octanuclear {[Mn III 3 Ca] 2 } cluster, alongside a structurally related trigonal prismatic naphthalene‐based triol ligand coordinated Mn III 6 Ca cage with magneto‐structural correlations [26] . Agapie's group recorded a major advancement by reporting two subsequent publications on rational synthesis and detailed analyses of Mn (III/IV) 3 Ca core supported by a ligand rich in pyridine nitrogen and phenolic OH [14,27] .…”

“…Escuer group constructed Mn II Mn III 3 Ca core by employing a Schiff base obtained through condensation between o ‐vanillin and ( R )‐ or ( S )‐phynylglycinol [31] . Amino acids also served as successful candidates for constructing Ca/Mn species, [Mn 3 III Ca II ] and [Mn III 6 Ca II ], with structural closeness to the OEC bearing weak anti‐ferro/ferro magnetic interactions within the metal centers [32] …”

“…[25] Recently this group divaulged an amino acid (Methylalanine) containing octanuclear {[Mn III 3 Ca] 2 } cluster, alongside a structurally related trigonal prismatic naphthalene-based triol ligand coordinated Mn III 6 Ca cage with magneto-structural correlations. [26] Agapie's group recorded a major advancement by reporting two subsequent publications on rational synthesis and detailed analyses of Mn (III/IV) 3 Ca core supported by a ligand rich in pyridine nitrogen and phenolic OH. [14,27] G. Christou and co-workers devised a synthetic model Mn IV 3 Ca assembled by means of pivalic acid which is followed by theoretical investigation.…”

“…[31] Amino acids also served as successful candidates for constructing Ca/Mn species, [Mn 3 III Ca II ] and [Mn III 6 Ca II ], with structural closeness to the OEC bearing weak anti-ferro/ferro magnetic interactions within the metal centers. [32] We intend to couple the facts: Mn/Ca cluster, partial similarity to distorted vacant cubane structure, bridged oxo/ hydroxo moiety, water ligand and chloride ions to shed light on the most desirable structure of OEC. Each tiny bit of advancement towards the understanding of structural pattern of the OEC is of tremendous significance for the scientific community.…”

Self-Assembled Heterometallic Complexes by Incorporation of Calcium or Strontium Ion into a Manganese(II) 12-Metallacrown-3 Framework Supported by a Tripodal Ligand with Pyridine-Carboxylate Motifs: Stability in Their Manganese(III) Oxidized Form

“…[13][14][15][16] Only few heterometallic manganese-calcium and manganese-strontium compounds have been isolated, and most examples have been published in the last ten years, reflecting a still largely unexplored area of research and also the synthetic difficulty to access such compounds. 1,[17][18][19][20][21][22][23][24][25][26][27][28][29] These complexes present a large variety of structures, topology and oxidation states, ranging from polymer to high nuclearity Mn 13 Ca 2 clusters and only a few of them are close structural mimics of the OEC. 24,28,[30][31][32][33] Among the synthetic Mn-Ca complexes, we have succeeded in the isolation of rare examples of carboxylate-bridged manganese(II)-calcium(II) complexes from the deprotonated tripodal tris(2-pyridylmethyl)amine hepta-and hexadentate ligands, tpaa 3-and tpada 2-, incorporating respectively three and two pyridine-carboxylate units: the tetranuclear [{Mn II (tpaa)} 2 {Ca(OH 2 ) 5 (μ-OH 2 )} 2 ] 2-(Mn 2 (tpaa) 2 Ca 2 (H 2 O) 12 ) and the dinuclear [Mn(tpada)ClCa(OH 2 ) 2.67 (MeOH) 2.33 ] -(Mn(tpada)Ca(H 2 O) 3 ) (Figure 1).…”