Solventless Supramolecular Chemistry via Vapor Diffusion of Volatile Small Molecules upon a New Trinuclear Silver(I)-Nitrated Pyrazolate Macrometallocyclic Solid: An Experimental/Theoretical Investigation of the Dipole/Quadrupole Chemisorption Phenomena

Abstract

A comparative study on the tendency of a new trinuclear silver(I) pyrazolate, namely, [N,N-(3,5-dinitropyrazolate)Ag]3 (1), and a similar compound known previously, [N,N-[3,5-bis(trifluoromethyl)pyrazolate]Ag]3 (2), to adsorb small volatile molecules was performed. It was found that 1 has a remarkable tendency to form adducts, at room temperature and atmospheric pressure, with acetone, acetylacetone, ammonia, pyridine, acetonitrile, triethylamine, dimethyl sulfide, and tetrahydrothiophene, while carbon monoxide, tetrahydrofuran, alcohols, and diethyl ether were not adsorbed. On the contrary, 2 did not undergo adsorption of any of the aforementioned volatile molecules. Adducts of 1 were characterized by elemental analysis, IR, thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) surface area, and diffusion NMR measurements. The crystal structures of 1·2CH3CN and compound 3, derived from an attempt to crystallize the adduct of 1 with ammonia, were determined by single-crystal X-ray diffractometric studies. The former shows a sandwich structure with a 1:2 stoichiometric [Ag3]/[CH3CN] ratio in which one acetonitrile molecule points above and the other below the centroid of the Ag3N6 metallocycle. Compound 3 formed via rearrangement of the ammonia adduct to yield an anionic trinuclear silver(I) derivative with an additional bridging 3,5-dinitropyrazolate and having [Ag(NH3)2](+) as the counterion, [Ag(NH3)2][N,N-(3,5-dinitropyrazolate)4Ag3]. Irreversible sorption and/or decomposition upon vapor exposure are desirable advantages toward toxic gas filtration applications, including ammonia inhalation. TGA confirms the analytical data for all of the samples, showing weight loss for each adsorbed molecule at temperatures significantly higher than the corresponding boiling temperature, which suggests a chemical-bonding nature for adsorption as opposed to physisorption. BET surface measurements of the "naked" compound 1 excluded physical adsorption in its porous cavities. Density functional theory simulation results are also consistent with the chemisorption model, explain the experimental adsorption selectivity for 1, and attribute the lack of similar adsorption by 2 to significantly less polarizable electrostatic potential and also to strong argentophilic bonding whose energy is even higher than the quadrupole-dipole adduct bond energy upon proper selection of the density functional.

Formation of a Fluorous/Organic Biphasic Supramolecular Octopus Assembly for Enhanced Porphyrin Phosphorescence in Air

“…[19,20] These data indicate the presence of strong dipole-quadrupole bonding of acetone and MeCN with Ag 3 in [2·Me 2 CO] and [2·MeCN],r espectively,a sd escribed in our recent work conducted in collaboration with the Burini and Galassi groups. [21] CO] followed by N 2 exposure,t he emission of PtOEP was recovered and gave the same emission profile as [2·(C 6 H 6 ) 1.5 ], which reinforces the aforementioned hypothesis that acetone and acetonitrile inclusion represents aquenching pathway whereas benzene inclusion represents as ensitizing pathway for porphyrin phosphorescence.…”

Formation of a Fluorous/Organic Biphasic Supramolecular Octopus Assembly for Enhanced Porphyrin Phosphorescence in Air

“…[19,20] These data indicate the presence of strong dipole-quadrupole bonding of acetone and MeCN with Ag 3 in [2·Me 2 CO] and [2·MeCN], respectively, as described in our recent work conducted in collaboration with the Burini and Galassi groups. [21] The strong interactions between the solvent molecules and 2 suggest that the [Ag 3 CO] followed by N 2 exposure, the emission of PtOEP was recovered and gave the same emission profile as [2·(C 6 H 6 ) 1.5 ], which reinforces the aforementioned hypothesis that acetone and acetonitrile inclusion represents a quenching pathway whereas benzene inclusion represents a sensitizing pathway for porphyrin phosphorescence.…”

“…[19,20] These data indicate the presence of strong dipole-quadrupole bonding of acetone and MeCN with Ag 3 in [2·Me 2 CO] and [2·MeCN],r espectively,a sd escribed in our recent work conducted in collaboration with the Burini and Galassi groups. [21] Thes trong interactions between the solvent molecules and 2 suggest that the [Ag 3 (m 1,2 -3,5-(n-C 3 F 7 ) 2 Tz) 3 ] macrocycles that bear af luorous octopus shell are strongly Lewis acidic/p-superacidic.Ananalysis of the crystal packing in [2·Me 2 CO] and [2·MeCN] (Figure 3) revealed small pores between the porphyrin alkyl chains,where gas molecules such as O 2 may reach exposed sides of the porphyrin plane.S uch interactions likely represent aprincipal cause for the emission quenching observed for [2·MeCN] and [2·Me 2 CO] in air, whereas guest inclusion of benzene molecules in [2·(C 6 H 6 ) 1.5 ] likely plays asensitizing/protecting role for the PtOEP triplet emission in air.Byapplying avacuum to crystals of [2·MeCN] and [2·Me 2 CO] followed by N 2 exposure,t he emission of PtOEP was recovered and gave the same emission profile as [2·(C 6 H 6 ) 1.5 ], which reinforces the aforementioned hypothesis that acetone and acetonitrile inclusion represents aquenching pathway whereas benzene inclusion represents as ensitizing pathway for porphyrin phosphorescence.…”

Argentophilic Interactions

“…[343][344][345] With very bulky substituents, the organization of the crystals is determined by other contacts where available, mainly between halogen atoms. [346] The arrangements are influenced not only by the substituent pattern of the individual components, but also by the presence of solvate molecules, [347] predominantly aromatic hydrocarbons. [348] The aromatic hydrocarbons become inserted between the stacked metallacycles leading to modified UV/ Vis absorption and emission properties, observed, for example, in the vapochromic behavior of the luminescent crystals of these compounds.…”