Nature of the coordination bond in metal complexes of substituted pyridine derivatives. II. The far infrared spectra and metal–ligand force constants of copper complexes of 4-substituted pyridines

Wong, P. T. T.; Brewer, D. G.

doi:10.1139/v68-025

Cited by 50 publications

(3 citation statements)

References 12 publications

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“…Back donation of Ni II to pyridines has been reported previously. [16,17] Cole et al determined the binding enthalpies of several pyridines to Fe IIporphyrins by optical spectroscopy. [18] They also observed that pyridine (R = H) was the weakest axial ligand, and electron-donating (e.g., R = NH 2 ) as well as electron-deficient substituents (e.g., R = CN) in the 4-position of the pyridine ligands gave rise to larger binding enthalpies, which led to a V shape of the DH versus pK a plot.…”

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confidence: 99%

Coordination‐Induced Spin Crossover (CISCO) through Axial Bonding of Substituted Pyridines to Nickel–Porphyrins: σ‐Donor versus π‐Acceptor Effects

Thies

Bornholdt

Köhler

et al. 2010

Chemistry A European J

120

158

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Nickel-porphyrins, with their rigid quadratic planar coordination framework, provide an excellent model to study the coordination-induced spin crossover (CISCO) effect because bonding of one or two axial ligands to the metal center leads to a spin transition from S=0 to S=1. Herein, both equilibrium constants K(1S) and K(2), and for the first time also the corresponding thermodynamic parameters DeltaH(1S), DeltaH(2), DeltaS(1S), and DeltaS(2), are determined for the reaction of a nickel-porphyrin (Ni-tetrakis(pentafluorophenyl)porphyrin) with different 4-substituted pyridines by temperature-dependent NMR spectroscopy. The association constants K(1S) and K(2) are correlated with the basicity of the 4-substituted pyridines (R: OMe>H>CO(2)Et>NO(2)) whereas the DeltaH(1S) values exhibit a completely different order (OMeCO(2)Et>NO(2)). 4-Nitropyridine exhibits the largest binding enthalpy, which, however, is overcompensated by a large negative binding entropy. We attribute the large association enthalpy of nitropyridine with porphyrin to the back donation of electrons from the Ni d(xz) and d(yz) orbitals into the pi orbitals of pyridine, and the negative association entropy to a decrease in vibrational and internal rotation entropy of the more rigid porphyrin-pyridine complex. Back donation for the nitro- and cyanopyridine complexes is also confirmed by IR spectroscopy, and shows a shift of the N-O and C-N vibrations, respectively, to lower wave numbers. X-ray structures of 2:1 complexes with nitro-, cyano-, and dimethylaminopyridine provide further indication of a back donation. A further trend has been observed: the more basic the pyridine the larger is K(1S) relative to K(2). For nitropyridine K(2) is 17 times larger than K(1S) and in the case of methoxypyridine K(2) and K(1S) are almost equal.

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confidence: 99%

Coordination‐Induced Spin Crossover (CISCO) through Axial Bonding of Substituted Pyridines to Nickel–Porphyrins: σ‐Donor versus π‐Acceptor Effects

Thies

Bornholdt

Köhler

et al. 2010

Chemistry A European J

120

158

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“…For all samples, the coordination of the metal ion to the electron‐rich segment of the copolymer, poly(2‐vinylpyridine), was supported by the decrease in the intensities of the peaks due to pyridine stretching and bending modes at 1594, 1472 and 1431 cm −1 and appearance of a new peak at 467 cm −1 . As an example, FTIR spectra of PS‐b‐P2VP and Cr‐PS‐b‐P2VP are given in Fig.…”

Section: Resultsmentioning

confidence: 87%

Preparation and thermal characterization of poly(2‐vinylpyridine) copolymers coordinated to Cr nanoparticles

Lekesiz

Kayran

Hacaloğlu

2015

Polymers for Advanced Techs

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In this study, polystyrene-block-poly(2-vinylpyridine), PS-b-P2VP, polyisoprene-block-poly(2-vinylpyridne), PI-b-P2VP and poly(methyl metacrylate)-block-poly(2-vinylpyridine), PMMA-b-P2VP, coordinated to Cr metal were synthesized and characterized by Fourier transform infrared, transmission electron microscopy and direct pyrolysis mass spectrometry techniques. Both thermal degradation mechanism and thermal stability of P2VP blocks were affected by the coordination of Cr nanoparticles to nitrogen of pyridine rings. Thermal decomposition of P2VP blocks was started by loss of pyridine units leaving an unsaturated and/or crosslinked polymer backbone that degraded at relatively high temperatures. Incorporation of Cr metal did not noticeably influence thermal behavior of PS and PI blocks. However, increase in thermal stability of PMMA block was detected and associated with inhibition of the interactions between carbonyl groups of MMA chains with nitrogen atom of pyridine ring as a consequence of coordination to metal.

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“…At this point, we want to emphasize that the applied computationally methodology is not set up to reproduce experimental results but to investigate the impact of TCNQ incorporation on the lattice dynamics qualitatively, thereby providing us with a scientific insight into the underlying changes in lattice dynamics. In a second step, we then gradually increased the force constant between k = 0−7 eV/Å 2 , typical values for Cu−N force constants 46 (Figure 3a). As compared to our experiment, this increase helps us to understand the impact of TCNQ on the lattice dynamics and is not designed to model the increasing TCNQ content.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Tuning the Negative Thermal Expansion Behavior of the Metal–Organic Framework Cu₃BTC₂ by Retrofitting

et al. 2019

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The modular building principle of metal− organic frameworks (MOFs) presents an excellent platform to explore and establish structure−property relations that tie microscopic to macroscopic properties. Negative thermal expansion (NTE) is a common phenomenon in MOFs and is often ascribed to collective motions that can move through the structure at sufficiently low energies. Here, we show that the introduction of additional linkages in a parent framework, retrofitting, is an effective approach to access lattice dynamics experimentally, in turn providing researchers with a tool to alter the NTE behavior in MOFs. By introducing TCNQ (7,7,8,8-tetracyanoquinodimethane) into the prototypical MOF Cu 3 BTC 2 (BTC = 1,3,5-benzenetricarboxylate; HKUST-1), NTE can be tuned between α V = −15.3 × 10 −6 K −1 (Cu 3 BTC 2 ) and α V = −8.4 × 10 −6 K −1 (1.0TCNQ@ Cu 3 BTC 2 ). We ascribe this phenomenon to a general stiffening of the framework as a function of TCNQ loading due to additional network connectivity, which is confirmed by computational modeling and far-infrared spectroscopy. Our findings imply that retrofitting is generally applicable to MOFs with open metal sites, opening yet another way to fine-tune properties in this versatile class of materials.

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Nature of the coordination bond in metal complexes of substituted pyridine derivatives. II. The far infrared spectra and metal–ligand force constants of copper complexes of 4-substituted pyridines

Cited by 50 publications

References 12 publications

Coordination‐Induced Spin Crossover (CISCO) through Axial Bonding of Substituted Pyridines to Nickel–Porphyrins: σ‐Donor versus π‐Acceptor Effects

Coordination‐Induced Spin Crossover (CISCO) through Axial Bonding of Substituted Pyridines to Nickel–Porphyrins: σ‐Donor versus π‐Acceptor Effects

Preparation and thermal characterization of poly(2‐vinylpyridine) copolymers coordinated to Cr nanoparticles

Tuning the Negative Thermal Expansion Behavior of the Metal–Organic Framework Cu₃BTC₂ by Retrofitting

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Nature of the coordination bond in metal complexes of substituted pyridine derivatives. II. The far infrared spectra and metal–ligand force constants of copper complexes of 4-substituted pyridines

Cited by 50 publications

References 12 publications

Coordination‐Induced Spin Crossover (CISCO) through Axial Bonding of Substituted Pyridines to Nickel–Porphyrins: σ‐Donor versus π‐Acceptor Effects

Coordination‐Induced Spin Crossover (CISCO) through Axial Bonding of Substituted Pyridines to Nickel–Porphyrins: σ‐Donor versus π‐Acceptor Effects

Preparation and thermal characterization of poly(2‐vinylpyridine) copolymers coordinated to Cr nanoparticles

Tuning the Negative Thermal Expansion Behavior of the Metal–Organic Framework Cu3BTC2 by Retrofitting

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Tuning the Negative Thermal Expansion Behavior of the Metal–Organic Framework Cu₃BTC₂ by Retrofitting