NICKEL(II) COMPLEXES OF TRIDENTATE <i>N,N,O</i>-DONOR LIGANDS: SYNTHESES, STRUCTURES AND REDOX PROPERTIES

Karunakar, Galla V.; Sangeetha, Nimma Rajaiah; Susila, Vishnubhatla; Pal, Samudranil

doi:10.1080/00958970008054924

Cited by 14 publications

(2 citation statements)

References 18 publications

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“…[24][25][26] The average N-C and C-O bond lengths in the -N=C(O -)-fragments [21][22][23][24][25][26] and the C-C and C-O bond lengths in the -C=C(O -)-fragments [21][22][23][24] are consistent with the enolate form of both amide and acetylacetone moieties of the tridentate ligands. …”

Section: Description Of X-ray Structures and C-h···ni Interactionsmentioning

confidence: 59%

Intramolecular Apical C–H···M Interactions in Square‐Planar Nickel(II) Complexes with Dianionic Tridentate Ligands and 2‐Phenylimidazole

Mukhopadhyay

Pal

2006

Eur J Inorg Chem

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Keywords: Nickel(II) complexes / Square-planar complexes / Apical C-H···Ni interactions / X-ray structures / Theoretical calculations and sp 2 N-donor 2-phenylimidazole (phim) as the ancillary ligand have been synthesised and characterised by analytical, spectroscopic, magnetic and electrochemical methods. The solid-state structures of both complexes have been determined by X-ray crystallography. The asymmetric unit of 1 contains a single complex molecule while that of 2 contains four complex molecules with different conformations. The molecular structures of both complexes reveal that one of the two ortho C-H groups of the pendant phenyl ring of the phim ligand is very close to the metal centre at the apical site indicating the presence of an intramolecular C-H···Ni interaction. In the structures of 1 and 2, the shape of the C-H···Ni interaction is determined by the twisting of the phim ligand and the extent of orthogo- IntroductionThe long standing interest in the interaction of transition metal ions with proximate C-H fragments is primarily due to the C-H activation processes involved in many catalytic reactions. Such interactions have been scrutinised intensively for a better understanding of their structural and bonding features. [1][2][3][4][5][6][7][8][9][10][11][12] The C-H···M interaction in coordinatively unsaturated and electron-deficient (16-electron) species is called an agostic interaction or agostic bond where the filled C-H σ orbital interacts with an empty metal orbital. In these agostic interactions, generally the C-H fragment is side-on to the metal ion. This T-shape of the agostic C-H···M interaction facilitates the involvement of the filled metal dπ orbital and the empty C-H σ* orbital in back bonding. However, the nature of the apical C-H···M interactions in square-planar 16-electron complexes of d 8 metal ions is not very clear. [9][10][11][12] In such species, these interactions can be agostic bond (three-centre two-electron) as well as non-classical hydrogen bond (three-centre four-elec- [a]

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Section: Description Of X-ray Structures and C-h···ni Interactionsmentioning

confidence: 59%

Intramolecular Apical C–H···M Interactions in Square‐Planar Nickel(II) Complexes with Dianionic Tridentate Ligands and 2‐Phenylimidazole

Mukhopadhyay

Pal

2006

Eur J Inorg Chem

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“…14,37 These parameters are smaller than the reported LS iron(II) analogues (Table S3), indicating a more regular geometry and a stronger ligand Interstitial solvent molecules were found for 2-Ni, and they were easily lost at room temperature. An overlay of the structures at 298 K 43 and 123 K (Figure 1d) shows consistent coordination environments and crystal packing. It is interesting to note that obvious motions were observed for the methoxyphenyl groups, indicating the flexibilities of these moieties.…”

Section: ■ Results and Discussionmentioning

confidence: 77%

Thermodriven, Acidity-Driven, and Photodriven Spin-State Switching in Pyridylacylhydrazoneiron(II) Complexes at or above Room Temperature

Shen

Zhang

et al. 2021

Inorg. Chem.

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The magnetic bistability of spin-crossover (SCO) materials is highly appealing for applications as molecular switches and information storage. However, switching of the spin state around room temperature remains challenging. In this work, we reported the successful manipulation of the spin states of two iron(II) complexes (1-Fe and 2-Fe) based on pyridylacylhydrazone ligands in manifold ways. Both complexes are stabilized in the lowspin (LS) state at room temperature because of the strong ligandfield strength imposed by the ligands. 2-Fe shows thermoinduced SCO above room temperature with a very large and reproducible hysteresis (>50 K), while 1-Fe remains in the LS state up to 400 K. Acidity-driven spin-state switching of the two complexes was achieved at room temperature as a result of the complex dissociation and release of iron(II) in its high-spin (HS) state. Recovery of the complex is feasible upon further alkalization treatment in the case of 1-Fe, allowing bidirectional modulation of the spin state of the metal center. Light-driven one-way switching from LS to HS is also achieved by virtue of E-to-Z isomerization at the CN double bond, which results in dissociation of the complex because of the poor binding affinity in the Z configuration.

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Structural Variations and Formation Constants of First‐Row Transition Metal Complexes of Biologically Active Aroylhydrazones

et al. 2003

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Iron chelators of the 2-pyridinecarbaldehyde isonicotinoylhydrazone (HPCIH) class show high potential for the treatment of iron overload diseases. In the present study, selected firstrow transition metal (from Mn to Zn) complexes with HPCIH and 2-pyridinecarbaldehyde (4Ј-aminobenzoyl)hydrazone (HPCAH) were synthesised and characterised. Crystallography reveals that HPCAH exclusively forms bis complexes with divalent transition metals, with each ligand coordinating meridionally through its pyridine-N, imine-N and carbonyl-O atoms, forming distorted octahedral cis-MN 4 O 2 complexes. Complexes of HPCIH were more varied and un-

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NICKEL(II) COMPLEXES OF TRIDENTATE N,N,O-DONOR LIGANDS: SYNTHESES, STRUCTURES AND REDOX PROPERTIES

Cited by 14 publications

References 18 publications

Intramolecular Apical C–H···M Interactions in Square‐Planar Nickel(II) Complexes with Dianionic Tridentate Ligands and 2‐Phenylimidazole

Intramolecular Apical C–H···M Interactions in Square‐Planar Nickel(II) Complexes with Dianionic Tridentate Ligands and 2‐Phenylimidazole

Thermodriven, Acidity-Driven, and Photodriven Spin-State Switching in Pyridylacylhydrazoneiron(II) Complexes at or above Room Temperature

Structural Variations and Formation Constants of First‐Row Transition Metal Complexes of Biologically Active Aroylhydrazones

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