A new NICS-based aromaticity index; NICS-rate

Influence of P‐Bonded Bulky Substituents on Electronic Interactions in Ferrocenyl‐Substituted Phospholes

“…For 3b, as maller angle waso bservedt han those for 3c, 3d,a nd 3e, which indicated greater planarity of the heterocyclic ring. The angle (b)o fd eflection of the substituent's carbon atom at the phosphorus from the C2-P-C5 plane of the phosphole ring is more important for evaluating the aromaticity and de-scribes possible flattening of the pyramidal phosphorus environment.T his value is associatedw ith the pc haracter of the All hydrogen atomsa nd distorted atoms have been omitted for clarity.Selectedbondlengths [],angles [8], andtorsion angles [8]: 3b:P1 ÀC2 1.827(5), C2À C3 1.358 (7), C3ÀC4 1.434(8), C4ÀC5 1.350 (7),C5 ÀP1 1.829(5),C 1 ÀC2 1.464 (7), C5ÀC6 1.457 (7),P 1 ÀC21 1.814(6);C 2-P1-C5 91.2(2), C2-P1-C21 109.1(2), C21-P1-C5 101.9 (2). 3c:P1 ÀC2 1.797(2), C2ÀC3 1.353(3), C3ÀC4 1.440(3), C4ÀC5 1.357(3), C5ÀP1 1.803(2),C 1 ÀC2 1.459(3),C 5 ÀC6 1.462(3), P1ÀC21 1.823(2);C2-P1-C5 91.55(10), C2-P1-C21 111.58 (9), C21-P1-C5 109.67 (10).…”

“…The relaxed scan suggestst hat, as the aryl group migrates between the faces of the heterocycle, there is an initial concomitant move- Table 2. Selectedb ond lengths []; angles [8]; and the Bird index of 3b-e,1 -benzylphosphole [37] (7), and 1-(2,4,6-tri-tert-butylphenyl)-3-methylphosphole [33] (8 [a] a = Angle of deflectiono ft he phosphorus atom out of the dienic carbon plane.…”

“…The "aromaticity"o fp hospholes is one of the most investigated properties of these five-membered heterocycles. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] In contrast to other analoguesh eterocycles, such as pyrroles, most phospholes are non-or only slightly aromatic. [16][17][18] Phospholes exhibit ap yramidal phosphorus environment and ah ighi nversion barrier,w hereas in pyrroles ap lanar geometry is present due to the higher aromatic stabilization energy, which compensates for the energy required for planarization.…”

The properties of hydrogenated derivatives of the alkali atom coated clusters C6M6 (M=Li, Na): A density functional study

“…Lazzeretti et al [29] have pointed out that NICS(1) is more accurate than NICS (0) to characterize the molecular aromaticity. If NICS (1) [18] can be used to further determine the aromaticity. The proportion of maximum NICS-rate and minimum NICS-rate is defined as (min)…”

“…An assessment of the stability of the H 2 -bound C 6 M 6 (M=Li, Na) cluster in terms of an aromaticity criterion offers important insights into the possible use of the C 6 M 6 (M=Li, Na) structure as an effective hydrogen storage material. The cage aromaticity of the bare as well as hydrogen bound C 6 M 6 (M=Li, Na) cluster has been evaluated from the nucleus independent chemical shift [16] (NICS) values at any site computed by exploiting the procedure of Schleyer et al [17] and the NICS-rate defined by Noorizadeh et al [18] The second part shows the calculation details, the third part presents the results and discussion, and the conclusion is given in the fourth part.…”