We report on the successful on-surface polymerization reaction of codeposited zwitterionic quinones with Fe atoms on Au(110) at an appropriate temperature. The resulting covalent one-dimensional polymer chains arrange in a well-ordered two-dimensional (2D) structure as proven by scanning tunneling microscopy and low-energy electron diffraction. The ordered regions can reach the micrometer size. Furthermore, the electronic and magnetic properties of the zwitterionic quinoidal polymers on Au(110) were investigated using the density functional theory with an explicit inclusion of the Hubbard U term. The spin-polarized generalized gradient approximation plus U method (SGGA + U) has been used, and the freestanding isolated polymer chain, the 2D arrangement, and the adsorbed polymers have been calculated. From ab initio calculations, we predict the zwitterionic quinoidal polymer chains to be a one-dimensional spin crossover compound. For the freestanding chains, we find two local minima with comparable energies but different spin states: a high-spin state (S = 2 per Fe) with an Fe–Fe distance of 7.9 Å and an intermediate-spin state (S = 1) with an Fe–Fe distance of 7.72 Å. The experimental and theoretical results show that the substrate dictates the lattice constant, and the adsorbed polymer on Au(110) has an Fe–Fe distance of 8.16 Å and is in the high-spin state. The exchange coupling in the polymeric chain with the Au(110) lattice constants was found to be antiferromagnetic. The adsorption on Au(110) removes the surface reconstruction of a free surface, and the ab initio simulation gives the short-bridge position for Fe as the most stable one.

Ab initio calculations based on density functional theory (DFT) including an explicit treatment of the strong electron correlation in the d shell of the transition metal ions have been conducted using the spin-polarized generalized gradient approximation with Hubbard term U (SGGA+U) to investigate systematically the electronic and magnetic properties of a new material class representing one-dimensional transition metal zwitterionic quinone (TM-ZQ) polymers having many potential applications, especially in spintronics. The complete class of 3d transition metals (TMs) are investigated from Sc to Zn. Zn-ZQ is nonmagnetic, since it has a 3d 10 configuration. All of the other TM-ZQ polymers are antiferromagnetic semiconductors with the exception of Mn-ZQ that is metallic for the ferromagnetic (FM) and the antiferromagnetic (AFM) spin arrangements and Sc-ZQ and Ti-ZQ which are FM semiconductors. All of these polymer chains have the potential to be produced by on-surface synthesis on metallic surfaces, as was recently shown for Fe-ZQ et al. Nano Res. 2017, 10, 933−940).

These field dependent molecular properties are of vital scientific and technological importance in the realm of photonics since they govern the non-linear optical behavior of molecules and materials. 18 Based on the above hypothesis and relying on previous experience in nanographene systems, 19,20,21 in this work we open the subject of the non-linear optical properties of PAHs and nanographenes doped with boron nitrogen dative bonds. A dative bond 22,23 denoted in the literature as D→A, is formed between two fragments, one playing the role of an electron donor (D) and the other role an acceptor (A). In terms of simplified valence bond theory, within a dative bond, the donor atom offers an entire "pair of electrons" to