Unusual Inorganic Biradicals: A Theoretical Analysis

Abstract

Der Biradikal‐Charakter β (mit 1 für ein ideales Biradikal) wird aus Multireferenz‐Konfigurationswechselwirkungs(MRCI)‐Wellenfunktionen bestimmt. Für die dreiatomigen Ionen der Reihe FX2+ (X=O, S, Se, Te, Po) ergeben sich mit 0.76–0.92 die höchsten β‐Werte unter den homologen 18‐Valenzelektronen‐Molekülen, verglichen mit CX22−, NX2−, X3 und OX2. Auf derselben Skala beträgt der Biradikal‐Charakter von O3 lediglich 0.19, C(CH2)3 erreicht hingegen einen Wert von 0.97.

Zwitterionic and biradicaloid heteroatomic cyclopentane derivatives containing different group 15 elements

“…Therefore, as illustrated in Scheme 6 and Table 1 , the zwitterionic character increases (biradical character decrease) along E 1 = As < P < N and E 2 = Sb < As < P. For example, a biradical character β of only 13% was computed for 2NP and 11% for 2NAs , respectively (CASSCF(6,6), coefficients of main contributions 0.946, –0.250 for 1NP and 0.956, –0.229 for 1NAs ). 58 However, 2PAs features substantial biradical character of β = 24% (CASSCF(6,6), c 1 = 0.916 and c 2 = –0.339), in agreement with the experimental fact that this species is capable of activating molecules containing triple bonds ( vide supra ) contrary to 2NP or 2NAs . Moreover, the larger zwitterionic character of 2NAs compared to 2PAs is also manifested by the HOMO of 2NAs featuring very large coefficients at As and very small ones at N, while for 2PAs the contributions are distributed almost evenly.…”

“…The biradicaloid character can be estimated by using the formula: β = 2 c 2 2 /( c 1 2 + c 2 2 ). 58 Hence, upon insertion of the isonitrile into the four-membered ring of 1 the biradical character is preserved compared to the starting material 1E 1 E 2 . Therefore, as illustrated in Scheme 6 and Table 1 , the zwitterionic character increases (biradical character decrease) along E 1 = As < P < N and E 2 = Sb < As < P. For example, a biradical character β of only 13% was computed for 2NP and 11% for 2NAs , respectively (CASSCF(6,6), coefficients of main contributions 0.946, –0.250 for 1NP and 0.956, –0.229 for 1NAs ).…”

Activation of Small Molecules by Phosphorus Biradicaloids

“…The quantity b = 2c 2 2 /(c 1 2 + c 2 2 ) = 0.25 agrees well with values found, for example, for ozone with b = 0.19 and can be used as a good measure of the biradical character. [81] Hence, it can be concluded that 2Ter possesses considerable biradical character, which we wanted to utilize in synthesis, especially for the activation of small molecules bearing single and multiple bonds, respectively.…”

Density functional theory study of oxygen migration in molten carbonate

“…To illustrate the mechanism and energetics of oxygen migration in different molten carbonate salts, accuracy and reliability of calculated energies are the key and of great importance. Both the structures of trasition state and CO 4 2are ozone-like, so they may have considerable biradical character [35][36][37][38]. The results from the B3LYP/6-31G(d) will need to be verified by higher level of theoretical methods.…”