Abstract: Aromatic, substituted pyrimidine compounds, methods for the preparation thereof, and use thereofCompounds having a pyrimidine ring, of the formula (I) ##STR1## are suitable for nonlinear-optical applications, e.g. for fabricating components for frequency-doubling of light. In the formula, AX is ##STR2## An.sup.- is an anion, B is the pyrimidine(1,4) radical, D is --NH.sub.2, --NH--NH.sub.2, --OR.sup.6, --O(CH.sub.2).sub.p OH, --OH, --NR.sup.5 R.sup.6, --NHR.sup.6, --N.dbd.CH--R.sup.4, --HN--N.dbd.CH--R.sup.4, --NO.sub.2,the radicals R.sup.1, R.sup.2, R.sup.3 and R.sup.5 are an alkyl radical having from 1 to 22 carbon atoms or a radical CF.sub.3 (CF.sub.2).sub.m (CH.sub.2).sub.n, R.sup.4 is a phenyl radical which may be substituted, R.sup.6 is an alkyl radical having from 1 to 22 carbon atoms or the radical CF.sub.3 (CF.sub.2).sub.m (CH.sub.2).sub.n, where m is an integer of at least 5, n is an integer of at least zero, and (n+m) is at most 22, or the group (CH.sub.2).sub.