Comounds having the formula ##STR1## wherein: a is 2 or 3; b is an integer from 0 to 4; Me.sup.(a+) is an ion of an element of atomic number from 57 to 70 or an ion of a transition metal of atomic number 21-29, 42 or 44; E.sup.(b+) is one or more physiologically biocompatible cation of an inorganic or an organic base or amino acid, said cation representing a total positive charge of b units; S is the group --A--O--R wherein: A is --(CH.sub.2).sub.m --; --CH.sub.2 --C(CH.sub.3).sub.2 --; m is an integer from 1 to 5; R is H; linear or branched alkyl of 1 to 8 carbon atoms, said carbon atoms being unsubstituted or substituted by one or more hyroxy group; aralkyl of 1 to 4 aliphatic carbon atoms; phenyl or phenyl substituted by halogen, amino, hydroxy or trifluoromethyl; (poly)-oxa-alkyl of 1 to 10 oxygen atoms and from 3 to 30 carbon atoms; R.sub.1 is R.sub.2 or --CH.sub.2 COOZ; --CH(CH.sub.3)COOZ; --(CH.sub.2).sub.n --N(CH.sub.2 COOZ).sub.2 ; hydroxy-arylalkyl radical in which the aryl radical is unsubstituted or substituted by hydroxy; R.sub.2 is --CH.sub.2 COOZ; --CH(CH.sub.3)COOZ; with the proviso that when R.sub.1 is --CH.sub.2 COOZ or --CH(CH.sub.3)COOZ, R.sub.2 is other than --CH.sub.2 COOZ and --CH(CH.sub.3)--COOZ ##STR2## wherein: R.sub.3 is --CH.sub.2 COOZ; --CH(CH.sub.3)COOZ; a monovalent radical having the structure S--CH--COOZ; X is a direct chemical bond; --O--; --S--; --NH--; --N--CH.sub.2 COOZ; --N--CH(CH.sub.3)COOZ; n is the integer 2 or 3, with the proviso that when X is a direct chemical bond, n is 1, 2 or 3; Z is H or a negative charge; with the proviso that, unless R represents a trifluoromethyl substituted phenyl or R.sub.1 is R.sub.2, Me.sup.(a+) is different from Fe.sup.(2+), Fe.sup.(3+), Gd.sup.(3+) and Mn.sup.(2+) and with the proviso that when R.sub.1 is R.sub.2 every molecule can contain not more than 500 nitrogen atoms.
具有以下公式的化合物##STR1##其中:a为2或3;b为0到4的整数;Me.sup.(a+)是原子序数为57到70的元素离子或原子序数为21-29、42或44的过渡
金属离子;E.sup.(b+)是一种或多种生理
生物相容的阳离子,可以是无机或有机碱或
氨基酸,该阳离子代表b个单位的总正电荷;S是基团--A--O--R,其中:A为--(CH.sub.2).sub.m --;--CH.sub.2 --C(CH.sub.3).sub.2 --;m为1到5的整数;R为H;线性或支链烷基,碳原子数为1到8,所述碳原子未被取代或被一个或多个羟基取代;1到4个脂肪碳原子的芳基烷基;苯基或苯基取代为卤素、
氨基、羟基或三
氟甲基;1到10个氧原子和3到30个碳原子的(聚)-氧烷基;R.sub.1为R.sub.2或--CH.sub.2 COOZ;--CH(CH.sub.3)COOZ;--(CH.sub.2).sub.n --N(CH.sub.2 COOZ).sub.2;带有羟基的芳基烷基基团,其中芳基未被取代或被羟基取代;R.sub.2为--CH.sub.2 COOZ;--CH(CH.sub.3)COOZ;但要求当R.sub.1为--CH.sub.2 COOZ或--CH(CH.sub.3)COOZ时,R.sub.2不是--CH.sub.2 COOZ和--CH(CH.sub.3)--COOZ之一##STR2##其中:R.sub.3为--CH.sub.2 COOZ;--CH(CH.sub.3)COOZ;具有结构S--CH--COOZ的一价基团;X为直接
化学键;--O--;--S--;--NH--;--N--CH.sub.2 COOZ;--N--CH(CH.sub.3)COOZ;n为整数2或3,但要求当X为直接
化学键时,n为1、2或3;Z为H或负电荷;但要求,除非R代表三
氟甲基取代苯基或R.sub.1为R.sub.2,否则Me.sup.(a+)不同于Fe.sup.(2+)、Fe.sup.(3+)、Gd.sup.(3+)和Mn.sup.(2+),且要求当R.sub.1为R.sub.2时,每个分子中不含有500个以上的氮原子。