High gain cobalt(III)complex composition and element

A radiation-sensitive element exhibiting upon exposure an internal gain, comprising a support and, as a coating thereon, a radiation-sensitive layer comprising, in admixture,

• a compound containing a conjugated .pi.-bonding system capable of forming a tridentate chelate with cobalt(III), said compound being defined by one of the formulas:
• Z.sup.2 --N.dbd.N --Z.sup.3,
• z.sup.4 --ch.dbd.n--nh--z.sup.5 or
• Z.sup.6 --CH.dbd.N--Z.sup.7
• wherein Z.sup.2, Z.sup.3, Z.sup.4, Z.sup.5, Z.sup.6, and Z.sup.7 are independently chosen from among 2-hydroxy, carboxy or amino substituted naphthyl or phenyl;
• 2-pyridyl;
• 2-quinolinyl;
• 2-thiazolyl;
• 2-benzothiazolyl;
• 2-oxazolyl;
• and 2-benzoxazolyl groups, and are each capable of forming chelate ligands, and
• an inert cobalt(III)complex capable of being reduced by a cobalt(III)complex containing said chelating compound,
• less than 50 mole percent of any acid anions of said layer being those having pKa values greater than 3.5.

A radiation-sensitive composition exhibiting upon exposure an internal gain and comprising, in admixture,

• a compound containing a conjugated .pi.-bonding system capable of forming a tridentate chelate with cobalt(III), said compound being defined by one of the formulas:
• Z.sup.2 --N.dbd.--Z.sup.3,
• z.sup.4 --ch.dbd.n--nh--z.sup.5 or
• Z.sup.6 --CH.dbd.N--Z.sup.7
• wherein Z.sup.2, Z.sup.3, Z.sup.4, Z.sup.5, Z.sup.6, and Z.sup.7 are independently chosen from among 2-hydroxy, carboxy or amino substituted naphthyl or phenyl;
• 2-pyridyl;
• 2-quinolinyl;
• 2-thiazolyl;
• 2-benzothiazolyl;
• 2-oxazolyl;
• and 2-benzoxazolyl groups, and are each capable of forming chelate ligands, and
• an inert cobalt(III)complex capable of being reduced by a cobalt(II)complex containing said chelating compound,
• less than 50 mole percent of any acid anions of said composition being those having pKa values greater than 3.5.

A radiation-sensitive composition exhibiting upon exposure an internal gain and comprising, in admixture,

• a cobalt(III)complex which is a hexa-ammine cobalt(III), penta-ammine cobalt(III), bis(ethylenediamine) cobalt(III), tris(ethylenediamine) cobalt(III), bis(propylene cobalt(III), tris(propylene) cobalt(III), bis(dimethylglyoxime) cobalt(III), cobalt(III) acetylacetonate or bis(2,2'-bipridyl) cobalt(III) complex and
• a compound containing a conjugated .pi.-bonding system capable of forming a tridentate chelate with cobalt(III), said compound being a 1-(2-pyridyl, 2-quinolinyl, 2-thiazolyl, 2-benzothiazolyl, 2-oxazolyl or 2-benzoxazolyl) formazan dye;
• a 1-(2-pyridyl, 2-quinolinyl, 2-thiazolyl, 2-benzothiazolyl, 2-oxazolyl or 2-benzoxazolyl)azo-2-(phenol or naphthol);
• 2-pyridinecarboxylaldehyde-(2-pyridyl, 2-quinolinyl, 2-thiazolyl, 2-benzothiazolyl, 2-oxazolyl or 2-benzoxazolyl) hydrazone;
• or 1-(2-pyridyl, 2-quinolinyl, 2-thiazolyl, 2-benzothiazolyl, 2-oxazolyl or 2-benzoxazolyl)-dithiooxamide;
• less than 50 mole percent of the acid anions of said composition being those having pKa values greater than 3.5.