A series of porphyrin derivatives <b>2a–f</b> was synthesized, namely, 5,10,15,20-<i >meso</i>tetrakis[<i >p</i>-methoxyphenyl]-21<i >H</i>,23<i >H</i>-porphyrin (<b >2a</b>), 5,10,15,20-<i >meso</i>tetrakis[2,6-dichloro-phenyl]-21<i >H</i>,23<i >H</i>-porphyrin (<b >2b</b>), 5,10,15,20-<i >meso</i>tetrakis[4-hydroxy-3,5-dimethoxyphenyl]-21<i >H</i>,23<i >H</i>-porphyrin (<b >2c</b>), 5,10,15,20-<i >meso</i>tetrakis[3,4-dimethoxyphenyl]-21<i >H</i>,23<i >H</i>-porphyrin (<b >2d</b>), 5,10,15,20-<i >meso</i>tetrakis[2,4-dichlorophenyl]-21<i >H</i>,23<i >H</i>-porphyrin (<b >2e</b>), and 5,10,15,20-<i >meso</i>tetrakis[3,4,5-trimethoxyphenyl]-21<i >H</i>,23<i >H</i>-porphyrin (<b >2f</b>), in high yields using a new method via a capping mechanism. These dyes were used as a model to study the free radical-induced damage of biological membranes and the protective effects of these porphyrins. It was demonstrated that these dyes were effective in the inhibition of the free radical-induced oxidative haemolysis of rat blood cells. Dyes <b >2d</b> and <b >2f</b> which bear methoxy functionality exhibited markedly higher antihaemolysis activity than the other analogs. Molecular modeling methods using ZINDO/INDO-1, with a configuration interaction of 26, and TD-DFT using the energy functional B3LYP and the basis set DGTZVP were used to study the vertical electronic excitations of porphyrins <b >2a–f</b> and it was shown that the <svg style="vertical-align:-3.39069pt;width:30.674999px;" id="M1" height="16.450001" version="1.1" viewBox="0 0 30.674999 16.450001" width="30.674999" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(.017,-0,0,-.017,.062,12.162)"><path id="x1D706" d="M529 97q-70 -109 -136 -109q-41 0 -56 94q-23 144 -37 284q-38 -88 -99 -202.5t-93 -156.5q-26 -8 -76 -19l-9 21q71 78 145.5 193t124.5 232q-5 84 -15 128q-12 55 -29.5 75.5t-42.5 20.5q-21 0 -45 -13l-8 24q16 17 46 30t55 13q43 0 70 -46.5t40 -169.5
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t-52 18.5v23q79 14 139 41v-81q3 2 29 20.5t44 29.5q45 28 81 28t66 -22t46 -61q25 20 83 57q39 26 76 26q59 0 93 -40t34 -113v-193q0 -49 10.5 -60.5t54.5 -16.5v-26z" /></g><g transform="matrix(.012,-0,0,-.012,19.159,16.25)"><path id="x61" d="M433 39l-85 -51q-27 0 -47 20q-16 16 -24 44q-5 -3 -24 -16.5t-27 -18.5t-23 -13.5t-25 -12t-19 -3.5q-52 0 -86 36.5t-34 85.5q0 71 81 99q128 43 155 65v17q0 54 -23 83.5t-62 29.5q-28 0 -45 -19t-29 -66q-7 -23 -29 -23q-15 0 -29 13t-14 30t31 40q25 19 68.5 40.5
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