Orbital energy mismatch engenders high-spin ground states in heterobimetallic complexes

Abstract

The spin state in heterobimetallic complexes heavily influences both reactivity and magnetism. Exerting control over spin states in main group-based heterobimetallics requires a different approach as the orbital interactions can...

Spectroscopic and Magnetic Studies of Co(II) Scorpionate Complexes: Is There a Halide Effect on Magnetic Anisotropy?

“…24−31 However, this correlation is not always observed. 32−34 To increase metal−ligand covalency, 3d complexes have also been prepared using ligands that feature more electropositive donor atoms from group 14 (Ge, Sn), 22,35,36 group 15 (As, Sb), 37,38 and group 16 (Se, Te). 39−42 This strategy has yielded mixed results, as the impact of the heavy-atom donors on |D|-values is sometimes modest.…”

“…In this scenario, the relatively weak SOC of 3d transition-metal ions may be amplified through (partial) covalent bonding to heavy-atom donors with much larger SOC constants. − Such “heavy-atom effects” have been shown to enhance SOC-dependent photophysical processes, such as intersystem crossings between singlet and triplet states . In the realm of molecular magnetism, several groups have sought to increase the magnetic anisotropy of transition-metal complexes through the incorporation of heavy-atom donors. , The effectiveness of this approach has been demonstrated in multiple studies of M–X complexes (where X = Cl, Br, and I), which found that the magnitude of ZFS increases with halide size. − However, this correlation is not always observed. − To increase metal–ligand covalency, 3d complexes have also been prepared using ligands that feature more electropositive donor atoms from group 14 (Ge, Sn), ,, group 15 (As, Sb), , and group 16 (Se, Te). − This strategy has yielded mixed results, as the impact of the heavy-atom donors on | D| -values is sometimes modest . It is also challenging to ascertain if changes in anisotropy are due to heavy-atom effects or subtle changes in the ligand field, which is also a major contributor to magnetic anisotropy.…”

Metal–Metal BondUmpolungin Heterometallic Extended Metal Atom Chains

“… 17 − 19 Reversal of expected bond polarity, or umpolung , is also an important concept with impacts in organic synthesis, 20 − 27 catalysis, 6 , 28 − 32 frustrated Lewis pairs, 33 , 34 and bonding in main group chemistry. 35 − 37 Another area in which bond polarity plays an important but underappreciated role is in coordination compounds containing heterometallic metal–metal bonds. The recent explosion of interest in heterometallic compounds 38 − 45 has produced a number of systematic series that illustrate how polarity impacts heterometallic bonding generally.…”

“…Bond polarity is a fundamental property of chemical systems, with donor–acceptor interactions at the heart of acid–base reactions, − organic chemistry, , inorganic solid state chemistry, − and coordination chemistry. − For example, the modern lexicon of coordination chemistry now contains X-, L-, or Z-type ligands, which indirectly describes the polarity of a metal–ligand bond by identifying the donor and acceptor involved in the interaction. − Reversal of expected bond polarity, or umpolung , is also an important concept with impacts in organic synthesis, − catalysis, ,− frustrated Lewis pairs, , and bonding in main group chemistry. − Another area in which bond polarity plays an important but underappreciated role is in coordination compounds containing heterometallic metal–metal bonds. The recent explosion of interest in heterometallic compounds − has produced a number of systematic series that illustrate how polarity impacts heterometallic bonding generally.…”