Sublimation Study of Six 5-Substituted-1,10-Phenanthrolines by Knudsen Effusion Mass Loss and Solution Calorimetry

Bruno Brunetti; Andrea Ciccioli; Andrea Lapi; Aleksey V Buzyurov; Ruslan N Nagrimanov; Mikhail A Varfolomeev; Stefano Vecchio Ciprioti

doi:10.3390/e24020192

Sublimation Study of Six 5-Substituted-1,10-Phenanthrolines by Knudsen Effusion Mass Loss and Solution Calorimetry

Entropy (Basel). 2022 Jan 27;24(2):192. doi: 10.3390/e24020192.

Authors

Bruno Brunetti¹, Andrea Ciccioli², Andrea Lapi^{2

3}, Aleksey V Buzyurov⁴, Ruslan N Nagrimanov⁴, Mikhail A Varfolomeev⁵, Stefano Vecchio Ciprioti⁶

Affiliations

¹ Istituto per lo Studio dei Materiali Nanostrutturati, Consiglio Nazionale delle Ricerche, Dipartimento di Chimica, Sapienza Università di Roma, P.le A. Moro 5, 00185 Rome, Italy.
² Dipartimento di Chimica, Sapienza Università di Roma, P.le A. Moro 5, 00185 Rome, Italy.
³ Istituto per i Sistemi Biologici (ISB-CNR), Sede Secondaria di Roma-Meccanismi di Reazione, Dipartimento di Chimica, Università degli Studi di Roma "La Sapienza", P.le A. Moro 5, 00185 Rome, Italy.
⁴ A.M. Butlerov Chemical Institute, Kazan Federal University, Kremlevskaja Str. 18, 420008 Kazan, Russia.
⁵ Department of Petroleum Engineering, Institute of Geology and Petroleum Technologies, Kazan Federal University, Kremlevskaja Str. 18, 420008 Kazan, Russia.
⁶ Dipartimento di Scienze di Base ed Applicate per l'Ingegneria (S.B.A.I.), Sapienza University of Rome, Via del Castro Laurenziano 7, Building RM017, 00161 Rome, Italy.

Abstract

The vapor pressures of six solid 5-X-1,10-phenanthrolines (where X = Cl, CH₃, CN, OCH₃, NH₂, NO₂) were determined in suitable temperature ranges by Knudsen Effusion Mass Loss (KEML). From the temperature dependencies of vapor pressure, the molar sublimation enthalpies, Δ_cr^gH_m⁰(⟨T⟩), were calculated at the corresponding average ⟨T⟩ of the explored temperature ranges. Since to the best of our knowledge no thermochemical data seem to be available in the literature regarding these compounds, the Δ_cr^gH_m⁰(⟨T⟩) values obtained by KEML experiments were adjusted to 298.15 K using a well known empirical procedure reported in the literature. The standard (p⁰ = 0.1 MPa) molar sublimation enthalpies, Δ_cr^gH_m⁰(298.15 K), were compared with those determined using a recently proposed solution calorimetry approach, which was validated using a remarkable amount of thermochemical data of molecular compounds. For this purpose, solution enthalpies at infinite dilution of the studied 5-chloro and 5-methylphenantrolines in benzene were measured at 298.15 K. Good agreement was found between the values derived by the two different approaches, and final mean values of Δ_cr^gH_m⁰(298.15 K) were recommended. Finally, the standard molar entropies and Gibbs energies of sublimation were also derived at T = 298.15 K. The volatilities of the six compounds were found to vary over a range of three orders of magnitude in the explored temperature range. The large difference in volatility was analyzed in the light of enthalpies and entropies of sublimation. The latter was tentatively put in relation to the rotational contribution of the substituent group on the phenanthroline unit.

Keywords: 5-substituted-1,10-phenanthrolines; Knudsen Effusion; entropic effect of rotation; solution calorimetry; standard molar sublimation Gibbs energies; standard molar sublimation enthalpy; standard molar sublimation entropy; vapor pressure.