Molecular tracers and modified proppants for monitoring underground fluid flows

1. A modified proppant, comprising:

a porous proppant; and

a metal ligand complex infused or impregnated in the porous proppant;

wherein the metal ligand complex is selected from the group consisting of [M(saloR′—R)(solv) x ] or [M(saloR′—R] without solvent attachments; and

wherein M is selected from the group consisting of alkali earth, transition, lanthanides, actinides and main group metals; and

wherein R is a bridging group selected from the group consisting of ethylene, phenylene, alkyl- or aryl-substituted phenylene, naphthyl and cyclohexyl; and

wherein R′ is a functional group selected from the group consisting of methyl, t-butyl, bromine, amino (—NR 2 ), nitrite (—NO 2 ), phosphonium (R 4 P + , derivatized sulfate (RSO 3 − ), halides (X) groups.

2. The modified proppant of claim 1 , wherein the proppant is porous.

3. The modified proppant of claim 1 , further comprising:

a polymer or resin in contact with the particulate or metal ligand complex.

4. The modified proppant of claim 1 , wherein the metal ligand complex comprises a ligand or ligand derivative selected from a group consisting of porphyrins, phthalocyanines or salens and their modified derivatives.

5. The modified proppant of claim 1 , wherein the metal ligand complex comprises a salen or salen derivative ligand.

6. The modified proppant of claim 1 , wherein the proppant is a porous ceramic particulate.

7. The modified proppant of claim 4 , wherein the ligand derivatives include attachment groups that modify the solubility of the metal ligand complex.

8. The modified proppant of claim 1 , wherein the metal is selected from the group consisting of Mg, Ca, Sc, Ti, Zr, Hf, V, Fe, Co, Ni, Zn, Al, Ga, and In.

9. The modified proppant of claim 1 , further comprising:

coating the porous proppant infused or impregnated with the metal ligand complex with a polymer or resin material.