Limits...
Crystal structure of BaMnB 2 O 5 containing structurally isolated manganese oxide sheets

View Article: PubMed Central - HTML - PubMed

ABSTRACT

In an attempt to search for mixed alkaline-earth and transition metal pyroborates, the title compound, barium manganese(II) pyroborate, has been synthesized by employing a flux method. The structure of BaMnB2O5 is composed of MnO5 square pyramids that form Mn2O8 dimers by edge-sharing and of pyroborate units ([B2O5]4−) that are composed of two corner-sharing trigonal–planar BO3 units. These building blocks share corners to form ∞2[MnB2O5]2− layers extending parallel to (100). The Ba2+ cations reside in the gap between two manganese pyroborate slabs with a coordination number of nine. The title compound forms an inter­esting spiral framework propagating along the 21 screw axis. The structure is characterized by two alternating layers, which is relatively rare among known transition-metal-based pyroborate compounds.

No MeSH data available.


(a) Extended structure of BaMnB2O5 viewed approximately along the [101] direction. The connectivity of the barium atoms is not shown for clarity. (b) Partial structure of [MnB2O5]2− slab viewed along [100] where the polyhedral drawing represents MnO5 square pyramids and B2O5 units are represented by ball-and-stick drawing. (c) Edge-sharing and corner-sharing MnO5 units corner-share with B2O5 pyroborate groups (polyhedral drawing) to create a cage. (d) Stick drawing of one cage with empty space in the middle.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5120715&req=5

fig4: (a) Extended structure of BaMnB2O5 viewed approximately along the [101] direction. The connectivity of the barium atoms is not shown for clarity. (b) Partial structure of [MnB2O5]2− slab viewed along [100] where the polyhedral drawing represents MnO5 square pyramids and B2O5 units are represented by ball-and-stick drawing. (c) Edge-sharing and corner-sharing MnO5 units corner-share with B2O5 pyroborate groups (polyhedral drawing) to create a cage. (d) Stick drawing of one cage with empty space in the middle.

Mentions: One of the inter­esting features of the title compound is that the structure can be alternatively viewed as a ‘porous’ framework as shown in Fig. 4 ▸a. The B2O5 units together with inter­connected Mn2O8 dimers extend along the b axis in a standing wave fashion, creating oval shape windows which also arrange in a zigzag fashion along the same direction. It is intriguing to notice that the two B2O5 groups along with the two Mn2O8 dimers and two MnO5 square pyramids create an empty cage (Fig. 4 ▸c,d). The polyhedral and ball-and-stick drawing (Fig. 4 ▸b) clearly shows the three-dimensional framework bearing large cavities. This unusual structural arrangement is conceivably attributed to the limitation of the size of the pyroborate unit that simultaneously tends to inter­connect with barium cations and neighboring Mn2O8 dimers in a corner-shared fashion (Fig. 3 ▸b). As shown in Fig. 5 ▸a, the layered nature of the title compound is characterized by parallel [MnB2O5]2− slabs outlined by a dotted rectangle viewed along [010]. Fig. 5 ▸b shows the ball-and-stick drawing of a portion of the layered manganese oxide network. Each Mn2O8 dimer shares vertices with four other MnO5 square pyramids through oxygen atoms to form these sheets. Within the extended Mn—O sheet, the MnO5 square pyramids which share edges are separated from each other by 3.317 (2) Å (Mn1⋯Mn1 distance) whereas those which share corners are separated by 3.435 (1) Å. The distance between the Mn atoms of the adjacent sheets is 8.287 (2) Å. Given the description of the local configuration of the manganese oxide polyhedra, their connectivity along the sheet, and the structural isolation of neighboring Mn—O sheets from each other, one would suspect that the title compound offers opportunities for the study of spin exchange in a confined Mn—O lattice. In theory, a periodic array of well-defined transition metal oxide lattices could provide a useful model for experimental and theoretical developments of magnetic and electronic inter­actions in transition metal oxides because of their simplified structures (Snyder et al., 2001 ▸).


Crystal structure of BaMnB 2 O 5 containing structurally isolated manganese oxide sheets
(a) Extended structure of BaMnB2O5 viewed approximately along the [101] direction. The connectivity of the barium atoms is not shown for clarity. (b) Partial structure of [MnB2O5]2− slab viewed along [100] where the polyhedral drawing represents MnO5 square pyramids and B2O5 units are represented by ball-and-stick drawing. (c) Edge-sharing and corner-sharing MnO5 units corner-share with B2O5 pyroborate groups (polyhedral drawing) to create a cage. (d) Stick drawing of one cage with empty space in the middle.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5120715&req=5

fig4: (a) Extended structure of BaMnB2O5 viewed approximately along the [101] direction. The connectivity of the barium atoms is not shown for clarity. (b) Partial structure of [MnB2O5]2− slab viewed along [100] where the polyhedral drawing represents MnO5 square pyramids and B2O5 units are represented by ball-and-stick drawing. (c) Edge-sharing and corner-sharing MnO5 units corner-share with B2O5 pyroborate groups (polyhedral drawing) to create a cage. (d) Stick drawing of one cage with empty space in the middle.
Mentions: One of the inter­esting features of the title compound is that the structure can be alternatively viewed as a ‘porous’ framework as shown in Fig. 4 ▸a. The B2O5 units together with inter­connected Mn2O8 dimers extend along the b axis in a standing wave fashion, creating oval shape windows which also arrange in a zigzag fashion along the same direction. It is intriguing to notice that the two B2O5 groups along with the two Mn2O8 dimers and two MnO5 square pyramids create an empty cage (Fig. 4 ▸c,d). The polyhedral and ball-and-stick drawing (Fig. 4 ▸b) clearly shows the three-dimensional framework bearing large cavities. This unusual structural arrangement is conceivably attributed to the limitation of the size of the pyroborate unit that simultaneously tends to inter­connect with barium cations and neighboring Mn2O8 dimers in a corner-shared fashion (Fig. 3 ▸b). As shown in Fig. 5 ▸a, the layered nature of the title compound is characterized by parallel [MnB2O5]2− slabs outlined by a dotted rectangle viewed along [010]. Fig. 5 ▸b shows the ball-and-stick drawing of a portion of the layered manganese oxide network. Each Mn2O8 dimer shares vertices with four other MnO5 square pyramids through oxygen atoms to form these sheets. Within the extended Mn—O sheet, the MnO5 square pyramids which share edges are separated from each other by 3.317 (2) Å (Mn1⋯Mn1 distance) whereas those which share corners are separated by 3.435 (1) Å. The distance between the Mn atoms of the adjacent sheets is 8.287 (2) Å. Given the description of the local configuration of the manganese oxide polyhedra, their connectivity along the sheet, and the structural isolation of neighboring Mn—O sheets from each other, one would suspect that the title compound offers opportunities for the study of spin exchange in a confined Mn—O lattice. In theory, a periodic array of well-defined transition metal oxide lattices could provide a useful model for experimental and theoretical developments of magnetic and electronic inter­actions in transition metal oxides because of their simplified structures (Snyder et al., 2001 ▸).

View Article: PubMed Central - HTML - PubMed

ABSTRACT

In an attempt to search for mixed alkaline-earth and transition metal pyroborates, the title compound, barium manganese(II) pyroborate, has been synthesized by employing a flux method. The structure of BaMnB2O5 is composed of MnO5 square pyramids that form Mn2O8 dimers by edge-sharing and of pyroborate units ([B2O5]4−) that are composed of two corner-sharing trigonal–planar BO3 units. These building blocks share corners to form ∞2[MnB2O5]2− layers extending parallel to (100). The Ba2+ cations reside in the gap between two manganese pyroborate slabs with a coordination number of nine. The title compound forms an inter­esting spiral framework propagating along the 21 screw axis. The structure is characterized by two alternating layers, which is relatively rare among known transition-metal-based pyroborate compounds.

No MeSH data available.