DFT and experimental studies on structure and spectroscopic parameters of 3,6-diiodo-9-ethyl-9H-carbazole

Abstract

The first report on crystal and molecular structure of 3,6-diiodo-9-ethyl-9H-carbazole is presented. Experimental room-temperature X-ray and 13 C chemical shift studies were supported by advanced theoretical calculations using density functional theory. The 13 C nuclear magnetic shieldings were predicted at the non-relativistic and relativistic level of theory using the zeroth-order regular approximation. Theoretical relativistic calculations of chemical shifts of carbons C3 and C6, directly bonded to iodine atoms, produced a reasonable agreement with experiment (initial deviation from experiment of 44.3 dropped to 4.25 ppm). The changes in ring aromatic character were estimated via a simple harmonic oscillator model of aromaticity and nucleus-independent chemical shift index calculations. A good linear correlation between experimental and theoretically predicted structural and NMR parameters was observed.

Method and basis set dependence of the NICS indexes of aromaticity for benzene

“…The NICS(0) was calculated in the middle of ring, and NICS(1) and its z‐component NICS(1) zz , were obtained 1 Å above the molecular plane. The latter parameters are more sensitive to the electronic structure . In addition, the position of NISC “ghost atom” or helium atom above the ring centre was changed from 10 to 0 Å.…”

“…In general, the above calculated NICS(0), NICS(1), and NICS(1)zz values for benzene are similar (not identical) to earlier reported magnetic indexes of aromaticity, obtained at the B3LYP/6−311++G(3df,2pd) level of theory . Interestingly, the largest differences in the calculated NICS parameters are between HF SCF and B3LYP (2.35, 1.27, and 3.35 ppm for NICS(0), NICS(1), and NICS(1)zz).…”

Computational 1H NMR: Part 1. Theoretical background

“…Relativistic effects in NMR chemical shifts and spinspin coupling constants known as "Heavy Atom on Light Atom" (HALA) effects were evaluated in a great number of molecules containing "heavy" elements, see some salient earlier publications [117][118][119][120][121][122][123][124][125][126] together with some more recent and most recent ones [127][128][129][130][131][132][133][134][135][136][137][138][139][140][141][142][143][144][145] and many other related papers, [146][147][148][149][150][151][152][153][154][155] which are not cited herewith in full in view of their multiplicity.…”

Solvent impact on the planarity and aromaticity of free and monohydrated zinc phthalocyanine: a theoretical study

“…Typically, NICS(0) was calculated in the middle of the subunit rings A, A1, B, and C (and directly in the ring plane), but similar results, called NICS(1) and its z-component NICS(1) zz , were obtained 1 Å above the molecular plane. The latter parameters are more sensitive to the electronic structure [69]. For comparison, HOMA and NICS values for individual ring subunits of planar H 2 Pc, pyrrole, indole, isoindole, and carbazole molecules were calculated.…”