The NQR Observation of Spin-Peierls Transition in an Antiferromagnetic MX-Chain Complex [NiBr(chxn)₂]Br₂

Abstract

81Br Nuclear quadrupole resonance (NQR) measurement was performed in an S = 1/2 one-dimensional Heisenberg antiferromagnetic metal complex [NiBr(chxn)2]Br2 (chxn: 1R,2R-diaminocyclohexane), having a halogen-bridged MX chain structure -Br-Ni3+-Br-Ni3+-Br-. Two 81Br NQR signals were observed below 40 K, while a single signal was observed above 130 K, showing the presence of two nonequivalent bridging Br sites below 40 K. This NQR result together with previously reported magnetic susceptibility and X-ray results indicate the occurrence of a transition into a spin-Peierls state between 40 and 130 K. This communication reports the first spin-Peierls transition in metal complexes in which pure d electrons contribute to the magnetism. In addition, we demonstrated a new experimental method for studying a spin-Peierls system.

One‐Dimensional Bromo‐Bridged NiIII Complexes [Ni(S,S‐bn)2Br]Br2 (S,S‐bn=2S,3S‐diaminobutane): Synthesis, Physical Properties, and Electrostatic Carrier Doping

“…[18] Figure 3 shows the temperature dependence of 81 Br NQR frequencies of the bridging Br ion in [NiA C H T U N G T R E N N U N G (S,S-bn) 2 Br]Br 2 and [NiA C H T U N G T R E N N U N G (chxn) 2 Br]Br 2 . [13] A single 81 Br NQR signal was observed at room temperature, which is consistent with X-ray crystal structure analysis that shows that all of the bridging Br sites are equivalent at room temperature. This equivalence indicates that [NiA C H T U N G T R E N N U N G (S,S-bn) 2 Br]Br 2 is in a Mott-Hubbard state.…”

“…Such behavior is consistent with that of [Ni-A C H T U N G T R E N N U N G (chxn) 2 Br]Br 2 . [13] A small amount of spin concentration that shows Curie-like behavior ( % 0.08 %) can be attributed to paramagnetic impurities; this is discussed in detail in the section on electrical conductivity. The weak temperature-dependent susceptibility at higher temperature ranges is interpreted as that of an S = 1 = 2 Heisenberg chain with quite a strong antiferromagnetic (AF) interaction.…”

“…The magnetic susceptibility slightly decreased below 100 K. Similar magnetic susceptibility behavior is observed in [NiA C H T U N G T R E N N U N G (chxn) 2 Br]Br 2 and can be explained by a spin-Peierls transition. [13] We have evaluated the magnetic susceptibility from ESR measurements, and not by using a Superconducting Quantum Interference Device (SQUID) for the following reasons: The magnetic susceptibility of this compound is very small ( % 10 À5 emu mol…”

Exploration of Boundary between Charge-Density-Wave and Mott–Hubbard States in Quasi-One-Dimensional Halogen-Bridged Metal Complexes

“…13 In the Ni complexes, many attractive physical properties have been reported such as gigantic third-order-nonlinear optical susceptibility, 14 spin-Peierls transition, 15 etc. To date, more than 300 MX-chain complexes have been reported.…”

Quasi‐Planar Organic Synthon and S···X (X = S or H–C) Contacts in Flat Copper Coordination Chains: Syntheses, Structures and Conductive Behaviour

“…productive approach towards conductive CPs, as exemplified by the well-known MX [8][9][10] or MMX chains (M = metal) [11][12][13][14][15] and "Shish-Kebab" molecular systems. [16] Moreover, CPs based on metal thiolate bonds have received long-standing interest because the π-donating character of the sulfur p orbital would improve metal-to-ligand electron exchange.…”