Electronic Structure and Properties of Bunz' Polymers

Abstract

The Bunz polymers consist of n-membered rings of carbon atoms connected via n monoor diethynyl units (m ) 1, 2 respectively) to other such rings. Coordinated to the three-, four-, and five-membered rings are ML n units (L ) CO, Cp) which lead to 18-electron rule stability at each metal-organic center. The electronic band structures of the metal-free (often metallic) and metal-complexed (always insulating) materials are derived, and it is shown how the insulating polymer-M(CO) 3 systems may be converted to systems with small bandgaps by the loss of a CO group. Depending on the width of the conduction band, either small bandgap semiconductors, ferromagnetic metals or antiferromagnetic insulators are predicted. The properties of C 6 ML x polymers are also investigated (ML x ) NO, CO, C 3 H 3 + ). These consist of an ML x unit attached to a graphite sheet. Bending the MNO group converts the linear three-electron donor "NO + " unit into an "NO -" moiety and generation of a metal. By construction of polymers with specific arrangements of M(CO) 3 and MCp groups, interesting patterns of metallic and insulating units may be envisaged at the atomic level.

Temporal evolution of composition and crystal structure of cobalt hexacyanoferrate nano-polymers synthesized in reversed micelles

“…We can also say that the existence of cetyltrimethylammonium cations (CTA) is the inevitable driving force in addition to halogen anions themselves. This can be confirmed by another reverse micellar synthesis of Fe-CN-Co MCNPs using a nonionic surfactant, NP-5 [35]; i.e., we could not create the structural conversion of Fe-CN-Co MCNPs in an NP-5 micellar solution dissolving CoCl 2 and K 3 [Fe III (CN) 6 ] as starting complexes, but generally produce it in the presence of CoCl 2 and (Et 4 N) 3 [Fe III (CN) 6 ] [50] after several hours of stirring. Therefore, tetraalkylammonium cations are simultaneously essential for the dehydration from Fe(Od)-CN-Co(Od) MCNPs to provoke the Fe(Od)-CNCo(Td) nanocrystal formation.…”

“…The general concept of these 3-D nets was first presented by Welles [1,2]. The geometries and connections created by selecting proper bridging ligands and metal ions produce novel functional materials with useful wide-ranging properties, e.g., electronic, magnetic, electrochromic, optical, catalytic, and adsorptive characteristics [3][4][5][6][7][8]. Among the metal coordination polymers, iron hexacyanoferrate, called Prussian blue, is the first metal coordination polymer used as an artificial dye in the 18th century.…”