“…According to earlier structural studies on several similar bisimidazoles exemplified in Chart , coplanar and straight (symmetric) connection is often accompanied by symmetric locations of NH hydrogen atoms, so that the electric polarities of the two imidazolyl units cancel one another out. The molecular structures are symmetric and nonpolar for 1 H ,1′ H -2,2′-biimidazole (Bim), 1 H ,1′ H -2,2′-bibenzimidazole (BBI), several 1 H ,1′ H -4,4′-biimidazole derivatives (R2-44Bim; R = H, Me, Et), − and two p -phenylene-bridged derivatives ( s -44Im2P and s -BI2P , ), whereas the o -phenylene- or methylene-bridged imidazoles Im2P and 44Im2C retain their polarity as a result of twisting of the two imidazolyl rings. The bridging spacers selected in the present study were o -phenylene (BI2P ( 1 ), TMBI2P ( 2 ), and BI2X ( 3 )), thien-2,5-diyl (BI2T ( 4 ) and TMBI2T ( 5 )), and 1 H -imidazole-4,5-diyl units (BI2Im ( 6 ), TMBI2Im ( 7 ), BI2MIm ( 8 ), and TMBI2MIm ( 9 )), which are expected to be bent, so as to eliminate inversion symmetry.…”