# $^{13}C-^{1}H$ HSQC experiment of probe molecules aligned in thermotropic liquid crystals: Sensitivity and resolution enhancement in the indirect dimension

Baishya, Bikash and Mavinkurve, Raghav G and Suryaprakash, N (2007) $^{13}C-^{1}H$ HSQC experiment of probe molecules aligned in thermotropic liquid crystals: Sensitivity and resolution enhancement in the indirect dimension. In: Journal of Magnetic Resonance, 185 (2). pp. 221-229.

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## Abstract

The spectra of molecules oriented in liquid crystalline media are dominated by partially averaged dipolar couplings. In the $^{13}C-^1H$ HSQC, due to the inefficient hetero-nuclear dipolar decoupling in the indirect dimension, normally carried out by using a \pi pulse, there is a considerable loss of resolution. Furthermore, in such strongly orienting media the $^1H-^1H$ and $^{13}C-^1H$ dipolar couplings leads to fast dephasing of transverse magnetization causing inefficient polarization transfer and hence the loss of sensitivity in the indirect dimension. In this study we have carried out $^{13}C-^1H$ HSQC experiment with efficient polarization transfer from $^1H$ to $^{13}C$ for molecules aligned in liquid crystalline media. The homonuclear dipolar decoupling using FFLG during the INEPT transfer delays and also during evolution period combined with the \pi pulse heteronuclear decoupling in the $t_1$ period has been applied. The studies showed a significant reduction in partially averaged dipolar couplings and thereby enhancement in the resolution and sensitivity in the indirect dimension. This has been demonstrated on pyridazine and pyrimidine oriented in the liquid crystal. The two closely resonating carbons in pyrimidine are better resolved in the present study compared to the earlier work [H.S. Vinay Deepak, Anu Joy, N. Suryaprakash, Determination of natural abundance $^{15}N-^1H$ and $^{13}C-^1H$ dipolar couplings of molecules in a strongly orienting media using two-dimensional inverse experiments, Magn. Reson. Chem. 44(2006) 553–565].

Item Type: Journal Article Copyright of this article belongs to Elsevier. HSQC spectrum;FSLG;FFLG;INEPTRD Division of Chemical Sciences > Solid State & Structural Chemistry UnitDivision of Physical & Mathematical Sciences > Physics 27 Jun 2008 19 Sep 2010 04:46 http://eprints.iisc.ernet.in/id/eprint/14652