Intertrimer and Intratrimer Metallophilic and Excimeric Bonding in the Ground and Phosphorescent States of Trinuclear Coinage Metal Pyrazolates:  A Computational Study

Abstract

The interactions present in cyclic trinuclear coinage metal pyrazolates were studied computationally. Cuprophilic interaction was found to bind the singlet ground state of the dimer of trimers {[Cu(Pz)] 3 } 2 , overcoming electrostatic repulsion. The large variation in intertrimer separations found in the literature for coinage metal pyrazolates is consistent with the relatively weak metallophilic interaction. The emissive triplet excited-state geometry of {[M(Pz)] 3 } 2 is predicted by density functional calculations to show major geometric distortion caused by Jahn-Teller instability and excimeric M-M bonding. Large calculated Stokes' shifts, which are also observed for experimental models, are consistent with significant excited-state distortions for these materials. The major finding derived from the present study is that the intertrimer M‚‚‚M contraction in the emissive T 1 state is much more than the intratrimer contraction in all {[M(Pz)] 3 } 2 models, giving rise to a lower T 1 f S 0 phosphorescence energy in these models than in analogous monomer-of-trimer models. The observations made here point to a great potential for rationally tuning the emission properties of trinuclear coinage metal complexes through choice of the metal and ligands.

Modeling the Deposition of Metal Atoms on a p-Type Organometallic Conductor: Implications for Stability and Electron Transfer

“…7,16,29 In addition, we also compared the geometries obtained from B3LYP with the B3PW91 30,31 hybrid functional (results not presented in the article) using the same basis set, which gave similar geometries for coinage metal-trimer complexes. In light of the study of Buhl et al on the geometries of transition metal complexes with different DFT functionals, [32][33][34] we selected the B3LYP functional for the current study.…”

Confined Metallophilicity within a Coordination Prism

“…Interestingly, all reported Cu 6 cases, including theoretical optimization [10] and experimental observation, [7][8][9]11] are found in the staggered mode (Figure 1) or in a combination of the eclipsed and staggered modes (usually called chair conformation)-no Cu 6 frontal mode has been documented so far, due to energetic and steric effects. Our presynthetic consideration for targeting the frontal mode involved the designer ligand L with bispyrazolate components for construction of Cu 3 units, two of which that were supposed to be fixed in a parallel fashion by three semirigid xylylene linkers with appropriate binding angles to yield a cageshaped Cu I -pyrazolate molecule with a prism conformation.…”

“…[5] Cotton and co-workers also claimed that their DFT calculations did not reveal any evidence for possible metal-metal bonding, despite very short Cu I -Cu I distances; hence contradicting the above-mentioned hybridization hypothesis. [6] The phenomenon of metallophilicity is usually encountered in coinage metal (Cu I , Ag I , and Au I ) compounds, [2] which include a classic family of cyclic, trinuclear, Cu I -pyrazolate complexes [7][8][9][10] (henceforth referred to as Cu 3 , see Figure 1) assembled through Cu I -Cu I interactions. Recently, such coinage-metal (Cu I and Ag I )-pyrazolate trimers were used by us [11] and others [12] as building blocks to assemble intriguing, supramolecular architectures.…”

“…Recently, such coinage-metal (Cu I and Ag I )-pyrazolate trimers were used by us [11] and others [12] as building blocks to assemble intriguing, supramolecular architectures. Note, in both oligomeric [7][8][9][10] and polymeric [11,12] Cu 3 -based aggregates, the intertrimeric Cu I -Cu I contact, rather than the intratrimeric one, functions as bright phosphor and features interesting luminescent behaviors [7][8][9] triggered by the unassisted dimer of trimers (henceforth referred to as Cu 6 , see Figure 1). Herein, we describe the design and synthesis of a new coordination prism, namely, [Cu 6 L 3 ] (L= p-xylylene-bis(3,5-dimethyl)pyrazol-4-yl), exhibiting an unprecedented Cu 6 stacking mode, with which we are able to capture structural and spectroscopic evidence of enhanced metallophilicity.…”

Arene‐Sandwiched Silver(I) Pyrazolates

“…Similar strong binding has been seen between [{(o-C 6 F 4 )Hg} 3 ] and arenes. [15,20] These contacts between the arene carbon atoms and the complex 1 are longer than the Ag I À C bonds of the arene adducts of ionic silver salts that usually show h 1 -or h 2 -bonded arenes with AgÀC distances ranging from 2.16(3) to 2.921 (9) . [30] Crystals of [(C 6 H 6 )(1)(C 6 H 6 )] lose some of the benzene molecules under reduced pressure at room temperature, thus In summary, herein we have described the isolation of sandwich molecules and supramolecular stacks which contain the acidic [{[3,5-(CF 3 ) 2 pz]Ag} 3 ] moiety and electron-rich aromatic p systems and in which the aggregation patterns depend on the solvent and the arene.…”