I am not an Applescript god but here is something that should work to convert the current date to the requested format and place it on the clipboard. I assumed you also wanted a dash between the hour and minute. If not, you can remove it.
set yearstr to year of (current date)
set monthnum to month of (current date) as integer
if monthnum < 10 then
set monthstr to "0" & (monthnum as string)
else
set monthstr to (monthnum as string)
end if
set daynum to (day of (current date)) as integer
if daynum < 10 then
set daystr to "0" & (daynum as string)
else
set daystr to (daynum as string)
end if
set t to time of (current date)
set hournum to (round (t / 3600) rounding down)
if hournum < 10 then
set hourstr to "0" & (hournum as string)
else
set hourstr to (hournum as string)
end if
set t to t - hournum * 3600
set minnum to (round (t / 60) rounding down)
if minnum < 10 then
set minstr to "0" & (minnum as string)
else
set minstr to (minnum as string)
end if
set t to t - minnum * 60
if t < 10 then
set secstr to "0" & (t as string)
else
set secstr to (t as string)
end if
set the clipboard to(yearstr & "-" & monthstr & "-" & daystr & "-" & hourstr & "-" & minstr & "-" & secstr) asstring