Systematic Design of Crystal Structure for Hofmann-Like Spin Crossover Fe(L)2[Ag(CN)2]2 Complexes

Takashi Kosone,Takeshi Kawasaki,Yoshinori Makido,Takafumi Kitazawa,Ayaka Haigo,Daisuke Akahoshi,Syogo Okuda,Toshiaki Saito

doi:10.3390/cryst9070370

Abstract

The synthesis, crystal structures, and magnetic properties of a new two-dimensional (2D) Hofmann-like series, FeII(L)2[AgI(CN)2]2 (L = 3-cyano-4-methylpyridine (1), allyl isonicotinate (2), phenyl-isonicotinate (3), and benzyl nicotinate (4)) were studied. These compounds have a 2D sheet structure because of their strongly determinate self-assembly process. An octahedral FeII ion is coordinated with the nitrogen atoms of[AgI(CN)2 linear units at equatorial positions and monodentate pyridine derivatives at the axial position. The layers construct a parallel stacking array. Compounds 1–3 show pairs of layers constructed by intermetallic Ag···Ag interactions. Compound 4 shows a mono-layer structure. The substituent bulk of the ligands affects the interlayer space. Compounds 1–4 undergo a 100% spin transition. However, compound 1, incorporating a smaller group, has a relatively lower critical temperature (Tc = 182 K (1), Tc = 221 K (2), Tc = 227 (3) and Tc1 = 236 K, Tc2 = 215 K (4)). We investigated the correlations between our systematic crystal design, substituent size, and the spin crossover profiles.

Highlights

Control of the self-assembly process enables the systematic design of supramolecular networks [1,2].In this respect, the Hofmann-like coordination polymer [3] is a strong tool due to its well-defined two-dimensional (2D) sheet structure
New 2D supramolecular networks [FeII(L)2[AgI(CN)2]2] exhibiting spin transitions were reported in this paper
We identified additional applicable ligands for constructing bilayer structures

Summary

Introduction

Control of the self-assembly process enables the systematic design of supramolecular networks [1,2]. In this respect, the Hofmann-like coordination polymer [3] is a strong tool due to its well-defined two-dimensional (2D) sheet structure. Many types of Hofmann-like coordination polymer using various metal ions and pyridine derivatives ligands have been derived. Since the first Hofmann-like spin crossover (SCO) coordination polymer {Fe(py)2 [Ni(CN)4 ]}n (py = pyridine) was reported [4], this structural motif has been frequently used to design Fe(II) SCO materials to enable us to determine the correlations between structural features and magnetic properties. Suppressing the structural diversity is required to systematically design the crystal structure and clarify the structure–property relationships

Methods

Results

Discussion

Conclusion