ZDC CTLR BECOMES DISTRED; ISSUING THE WRONG ALT ASSIGNMENT TO THE WRONG ACFT; CAUSING THE CONFLICTION.

Narrative

I WAS STEPPING DOWN ACFT X AND Y FOR APCHS; (DEN) AIRSPACE. FLT LEVEL 180 WAS UNUSABLE FOR STD SEPARATION. ACFT Y WAS DSNDING TO 16000 FT; AND ACFT X WAS DSNDING TO FL180. I WAS WORKING ALL AIRSPACE IN AREA EXCEPT FOR LOW ALT; SECTOR 36. THERE WAS A DISTURBANCE GOING ON IN THE AREA. THE SUPVR WANTED SECTORS BROKEN OUT. IT WASN'T AN APPROPRIATE TIME. I WENT TO CALL APCH TO REQUEST ACFT X AT 17000 FT ALT. (THE RESTR FOR HIS TYPE ACFT IS TO ENTER APCHS AIRSPACE AT 16000 FT.) APCH DID NOT ANSWER THE LINE. HE DISTURBANCE CONTINUED THROUGH OUT THIS PROCESS. WHEN I CONTACTED ACFT X; I CLRED HIM TO CROSS POWDER INTXN AT 16000 FT AND THEN SHIPPED HIM TO APCH. THEREFORE; STD SEPARATION WAS LOST. THERE ARE NUMEROUS FACTORS THAT CONTRIBUTED TO THIS EVENT. COMPLEX AIRSPACE COULD HAVE BEEN BROKEN OUT LESSENING THE WORK LOAD. TAKING THE LOUD CONVERSATION OUT OF THE CTL ROOM. POSSIBLE THAT THE RESTRICTION FOR ACFT X CAME OUT AS AN AUTOMATIC; DISREGARDING THE PREVIOUS INTENTION OF STOPPING ACFT X AT 17000 FT. LOOKING AT ACFT Y DATA BLOCK A GIVING THE ALT TO ACFT X.