Square-planar Transition-metal Complexes Research Articles

Controlling Film Formation and Host-Guest Interactions to Enhance the Thermoelectric Properties of Nickel-Nitrogen-Based 2D Conjugated Coordination Polymers.

2D conjugated coordination polymers (cCPs) based on square-planar transition metal-complexes (such as MO4, M(NH)4, and MS4, M = metal) are an emerging class of (semi)conducting materials that are of great interest for applications in supercapacitors, catalysis, and thermoelectrics. Finding synthetic approaches to high-performance nickel-nitrogen (Ni-N) based cCP films is a long-standing challenge. Here, a general, dynamically controlled on-surface synthesis that produces highly conductive Ni-N-based cCP films is developed and the thermoelectric properties as a function of the molecular structure and their dependence on interactions with ambient atmosphere are studied. Among the four studied cCPs with different ligand sizes hexaminobenzene- and hexaaminotriphenylene-based films exhibit record electrical conductivity (100-200 S cm-1) in this Ni-N based cCP family, which is one order of magnitude higher than previous reports, and the highest thermoelectric power factors up to 10 µW m-1 K-2 among reported 2D cCPs. The transport physics of these films is studied and it is shown that depending on the host-guest interaction with oxygen/water the majority carrier type and the value of the Seebeck coefficient can be largely regulated. The high conductivity is likely reflecting good interconnectivity between (small) ordered domains and grain boundaries supporting disordered metallic transport.

CO2 reduction catalysis by tunable square-planar transition-metal complexes: a theoretical investigation using nitrogen-substituted carbon nanotube models.

In this work, using density functional theory, we have characterized the CO2 reduction capabilities of a series of nine transition-metal-chelated nitrogen-substituted carbon nanotube models (TM-4N2v-CNT). Each of the chelated models consists of a four-N-substituted and one vacancy framework to mimic square planar homogeneous catalysts, and is coordinated to Fe, Ru, Os, Co, Rh, Ir, Ni, Pt or Cu. The results are further investigated to search for the possible electrochemical intermediates along the CO2 reduction pathway. We've found that all of the tested elements are predicted to favor the hydrogen evolution reaction over CO2 reduction energetically (with the exception of Cu), and that only Group 8 elements are predicted to bind CO effectively and other cases prefer HCOOH formation. The observed CO binding preference could be rationalized via ligand field theory based on the molecular orbitals of the square planar complexes. With a suitable applied voltage to stabilize all of the adsorbed CO intermediates, Ru and Os are predicted to produce CH4, whereas Fe is predicted to produce CH3OH. Increasing the curvature of the CNT could reduce the required potential in the potential-determining step substantially. However, the predicted catalytic sequence is subject to only the selection of a metal center.

Perfluoroalkylation of Square-Planar Transition Metal Complexes: A Strategy To Assemble Them into Solid State Materials with a π–π Stacked Lamellar Structure

Formation of π–π stacked lamellar structure is important for high performance organic semiconductor materials. We previously demonstrated that perfluoroalkylation of aromatics and heteroaromatics was one of the strategies to design organic crystalline materials with π–π stacked lamellar structures while improving air stability as a result of the strong electron withdrawing ability of perfluoroalkyl substituents. Square-planar transition metal complexes with large π-conjugated ligands are also an important category of semiconductor materials. We have perfluoroalkylated square-planar transition metal complexes, leading to the formation of a π–π stacked lamellar crystal packing motif in the solid state. Here we report six crystal structures of Pd and Pt complexes with bis-perfluorobutylated catechol ligand as one of the two ligands that bonds to the metal centers. This structural design possesses similar molecular topology when compared to perfluoroalkylated aromatics and heteroaromatics we have reported pre...

Structure, solvent, and relativistic effects on the NMR chemical shifts in square-planar transition-metal complexes: assessment of DFT approaches.

The role of various factors (structure, solvent, and relativistic treatment) was evaluated for square-planar 4d and 5d transition-metal complexes. The DFT method for calculating the structures was calibrated using a cluster approach and compared to X-ray geometries, with the PBE0 functional (def2-TZVPP basis set) providing the best results, followed closely by the hybrid TPSSH and the MN12SX functionals. Calculations of the NMR chemical shifts using the two-component (2c, Zeroth-Order Regular Approximation as implemented in the ADF package) and four-component (4c, Dirac-Coulomb as implemented in the ReSpect code) relativistic approaches were performed to analyze and demonstrate the importance of solvent corrections (2c) as well as a proper treatment of relativistic effects (4c). The importance of increased exact-exchange admixture in the functional (here PBE0) for reproducing the experimental data using the current implementation of the 2c approach is partly rationalized as a compensation for the missing exchange-correlation response kernel. The kernel contribution was identified to be about 15-20% of the spin-orbit-induced NMR chemical shift, ΔδSO, which roughly corresponds to an increase in ΔδSO introduced by the artificially increased exact-exchange admixture in the functional. Finally, the role of individual effects (geometry, solvent, relativity) in the NMR chemical shift is discussed in selected complexes. Although a fully relativistic DFT approach is still awaiting the implementation of GIAOs for hybrid functionals and an implicit solvent model, it nevertheless provides reliable NMR chemical shift data at an affordable computational cost. It is expected to outperform the 2c approach, in particular for the calculation of NMR parameters in heavy-element compounds.

Parallel stacking interactions in square-planar transition-metal complexes containing fused chelate and C6-aromatic rings

Stacking interactions in the crystal structures of square-planar transition metal complexes from the Cambridge Structural Database with five- and six-membered chelate rings fused with C(6-arom) rings (arom = aromatic) were analyzed. The distribution of distances between the closest C(6-arom)-C(6-arom) and C(6-arom)-chelate contacts shows that in a large fraction of the intermolecular interactions the C(6-arom) ring of one molecule is closer to the chelate than to the C(6-arom) ring of the other molecule. These results indicate a possible preference of the C(6-arom) ring to form stacking contacts with the chelate rings. The preference is ubiquitous and does not depend on the metal type.

Solvent Effects and Dynamic Averaging of 195Pt NMR Shielding in Cisplatin Derivatives

The influences of solvent effects and dynamic averaging on the (195)Pt NMR shielding and chemical shifts of cisplatin and three cisplatin derivatives in aqueous solution were computed using explicit and implicit solvation models. Within the density functional theory framework, these simulations were carried out by combining ab initio molecular dynamics (aiMD) simulations for the phase space sampling with all-electron relativistic NMR shielding tensor calculations using the zeroth-order regular approximation. Structural analyses support the presence of a solvent-assisted "inverse" or "anionic" hydration previously observed in similar square-planar transition-metal complexes. Comparisons with computationally less demanding implicit solvent models show that error cancellation is ubiquitous when dealing with liquid-state NMR simulations. After aiMD averaging, the calculated chemical shifts for the four complexes are in good agreement with experiment, with relative deviations between theory and experiment of about 5% on average (1% of the Pt(II) chemical shift range).

Evidence of Chelate−Chelate Stacking Interactions in Crystal Structures of Transition-Metal Complexes

Evidence of chelate−chelate stacking interactions was obtained by analyzing crystal structures of square-planar transition-metal complexes from the Cambridge Structural Database. The analysis showed that chelate−chelate stacking interactions occur in a large number of the crystal structures of neutral square-planar complexes. We found 955 structures with 1866 chelate−chelate stacking interactions. In most of the structures, chelate rings are fused with other chelate rings or with organic aromatic rings; however, chelate−chelate stacking interactions of isolated rings were also found. In order to describe the geometry of the chelate−chelate stacking interactions, several geometric parameters were analyzed. In most of the interactions, two chelate rings are in parallel or antiparallel orientation. The normal distances are similar to the distances of stacking interactions observed in other systems, while the offset of two interacting chelate rings can be different from that observed in other systems.

The Trans Effect: A Guided-Inquiry Experiment for Upper-Division Inorganic Chemistry

This article describes a guided-inquiry laboratory for upper-division inorganic chemistry. The experiment is designed to teach students about the trans effect through synthesis of the cis and trans geometric isomers of diamminedichloroplatinum(II). Students discover which factors lead to trans-substitution versus cis-substitution in square-planar transition-metal complexes. Student pairs are assigned a synthetic protocol, and product geometry is determined experimentally using a colorimetric thiourea test. Focus questions guide students to generate a trans-directing ligand series and to construct the trans effect concept. This experiment gives students technical experience in microscale inorganic synthesis and stereochemical analysis while teaching them about coordination chemistry and the importance of metals in medicine.

Ionic Interaction as a Powerful Driving Force for the Formation of Heterobidentate Assembly Ligands

An ionic interaction has been used for the first time to assemble monophosphane ligands. NMR spectroscopy and X-ray studies show that cationic and anionic triphenylphosphane derivatives form ion pairs and subsequently act as a ligand in various transition-metal complexes. The position of the ionic functional groups allows both cis and trans coordination of the novel assembly ligand in square-planar transition-metal complexes.

Influence of metal and ligand types on stacking interactions of phenyl rings with square-planar transition metal complexes

AbstractIn order to find out whether metal type influences the stacking interactions of phenyl rings in square-planar complexes, geometrical parameters for Cu, Ni, Pd and Pt complexes, with and without chelate rings, were analyzed and compared. By searching the Cambridge Structural Database, 220 structures with Cu complexes, 211 with Ni complexes, 285 with Pd complexes, and 220 with Pt complexes were found. The results show that the chelate ring has a tendency to make the stacking interaction with the phenyl ring independent of metal type in the chelate ring. However, there are some differences among metals for complexes without a chelate ring. There are a number of structures containing Pd and Pt complexes, without chelate rings, that have short carbon-metal distances and parallel orientations of the phenyl ring with respect to the coordination plane. It was found that some of these complexes have a common fragment, CN, as a part of the ligands. This indicates that the CN supports stacking interactions of square planar complexes with the phenyl ring.

Stacking vs. CH–π interactions between chelate and aryl rings in crystal structures of square-planar transition metal complexes

The crystal structures of square-planar transition-metal complexes from the Cambridge Structural Database (CSD) with close contacts between planar chelate rings and aryl rings containing six carbon atoms (C6-aryl) were analyzed. Most of the chelate rings in these structures are fused with aromatic or other π-delocalized chelate rings. The results show that planar chelate rings can be involved in stacking and CH–π interactions with organic aryl rings. However, the number of stacking interactions is a few times larger than the number of CH–π interactions. The analysis also shows that in almost all cases CH–π interactions are formed only when stacking interactions are prevented by voluminous substituents. Hence, between planar chelate rings and C6-aryl rings stacking interactions are preferred to CH–π interactions.

Stacking Interactions between Chelate and Phenyl Rings in Square-Planar Transition Metal Complexes

Analysis of geometrical parameters in the crystal structure of square-planar complexes, with and without chelate rings, of all transition metals from Cambridge Structural Database shows that there are stacking interactions between the phenyl ring and the chelate ring with delocalized π-bonds. Short distances between the metal and carbon atom of the phenyl ring and parallel orientation of phenyl ring with respect to the coordination plane were found in the crystal strucutres of complexes with chelate rings. There is a correlation of the distances between the centers of chelate and phenyl rings and the metal−carbon distances showing that the chelate and phenyl rings tend to overlap. In the crystal structures, there are mutual slipped-parallel orientations of the phenyl and chelate rings. The data show that the geometry of the stacking interaction between phenyl and chelate rings is similar to the geometry of the stacking interaction of two benzene rings, indicating that chelate rings can behave similarly to organic aromatic rings.

Theoretical studies of inorganic and organometallic reaction mechanisms. 2. The trans effect in square-planar platinum(II) and rhodium(I) substitution reactions

Ab initio calculations with an effective core potential have been used to study the mechanism of substitution reactions for square-planar transition-metal complexes. Pseudo-trigonal-bipyramidal transition states with rather small entering-ligand to metal to leaving-ligand angles were found for the substitution reactions investigated in this paper. The stability of the transition state is determined by both σ and π effects of the ligands

SHAPES empirical force field: new treatment of angular potentials and its application to square-planar transition-metal complexes

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSHAPES empirical force field: new treatment of angular potentials and its application to square-planar transition-metal complexesViloya S. Allured, Christine M. Kelly, and Clark R. LandisCite this: J. Am. Chem. Soc. 1991, 113, 1, 1–12Publication Date (Print):January 1, 1991Publication History Published online1 May 2002Published inissue 1 January 1991https://doi.org/10.1021/ja00001a001RIGHTS & PERMISSIONSArticle Views584Altmetric-Citations125LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

An investigation of the chelate effect: The binding of bidentate phosphine and arsine chelates in square-planar transition metal complexes

An investigation of the chelate effect: The binding of bidentate phosphine and arsine chelates in square-planar transition metal complexes

ChemInform Abstract: ON THE KINETIC TRANS EFFECT IN SQUARE PLANAR TRANSITION METAL COMPLEXES

Chemischer InformationsdienstVolume 5, Issue 36 Organoelement Compounds ChemInform Abstract: ON THE KINETIC TRANS EFFECT IN SQUARE PLANAR TRANSITION METAL COMPLEXES L. G. VANQUICKENBORNE, L. G. VANQUICKENBORNESearch for more papers by this authorJ. VRANCKX, J. VRANCKXSearch for more papers by this authorC. GOERLLER-WALRAND, C. GOERLLER-WALRANDSearch for more papers by this author L. G. VANQUICKENBORNE, L. G. VANQUICKENBORNESearch for more papers by this authorJ. VRANCKX, J. VRANCKXSearch for more papers by this authorC. GOERLLER-WALRAND, C. GOERLLER-WALRANDSearch for more papers by this author First published: September 10, 1974 https://doi.org/10.1002/chin.197436335AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume5, Issue36September 10, 1974 RelatedInformation

Electronic structure of square-planar transition metal complexes. I. Tetrachloroplatinate(2-) and tetrachloropalladate(2-) ions

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTElectronic structure of square-planar transition metal complexes. I. Tetrachloroplatinate(2-) and tetrachloropalladate(2-) ionsR. P. Messmer, L. V. Interrante, and K. H. JohnsonCite this: J. Am. Chem. Soc. 1974, 96, 12, 3847–3854Publication Date (Print):June 1, 1974Publication History Published online1 May 2002Published inissue 1 June 1974https://doi.org/10.1021/ja00819a024RIGHTS & PERMISSIONSArticle Views219Altmetric-Citations42LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (917 KB) Get e-Alerts Get e-Alerts

Question of the generality of symmetry rules for optically active, square-planar transition metal complexes

Question of the generality of symmetry rules for optically active, square-planar transition metal complexes