beginner issue with "unexpected token" error

Hi, 

I am trying to write my first powershell script but am completely stumped and trawling google hasn't helped.

I am writing (trying to write I should say) a script to look through a folder tree and identify photographs where the archive bit has been set and on those files run ImageMagick to convert the file to a different size.

My script is as follows and I've included how I am running the code 

 # Invokation :
# powershell -ExecutionPolicy RemoteSigned -File .\RI2.ps1

# ----------------------------------------
# Configuration
$srcfolder = "D:\TempFiles\PictureProcessing\PicsforDisplay"
$destpath = "D:\TempFiles\PictureProcessing\PicsforDisplay"
$im_convert_exe = "c:\program files (x86)\ImageMagick-6.8.6-Q16\convert.exe"
$src_filter = "*.jpg", "*.tif", "*.png"
$options = "-resize 1920x1080^>"
# ----------------------------------------

foreach ($srcitem in $(Get-ChildItem ${srcfolder} -include ${src_filter} -recurse | Where {$_.attributes -match "Archive"}))
{
    $srcname = ${srcitem}.fullname

    # Perform the conversion by calling an external tool
    $cmdline =  " `"" +${im_convert_exe} + "`"" + " `"" + ${srcname}  + "`"" + " "+ ${options} + " `"" + ${srcname} + "`" " 
	echo ${cmdline} 
	invoke-expression -command  ${cmdline}

}

When I run the script I get the error :

Invoke-Expression : Unexpected token 'D:\TempFiles\PictureProcessing\PicsforDis
play\Alex\2013\P1000985.JPG' in expression or statement.
At D:\Temp\test\2\RI2.ps1:23 char:19+     invoke-expression <<<<  -command  ${cmdline}+ CategoryInfo          : ParserError: (D:\TempFiles\Pi...13\P1000985.JPG:
   String) [Invoke-Expression], ParseException+ FullyQualifiedErrorId : UnexpectedToken,Microsoft.PowerShell.Commands.In
   vokeExpressionCommand

I get the error once for each file (so in this instance P1000985.jpg in the given folder).

The echo ${cmdline} entry outputs the actual text which I think is the text I am asking to be executed :

"c:\program files (x86)\ImageMagick-6.8.6-Q16\convert.exe" "D:\TempFiles\Pictu
reProcessing\PicsforDisplay\Alex\P1000885.JPG" -resize 1920x1080^> "D:\TempFile
s\PictureProcessing\PicsforDisplay\Alex\P1000885.JPG"

and if I copy that (and remove the newlines) it runs perfectly.

I'm not sure if that is enough for anyone to help me - am I doing something incredibly dumb? Clearly I'm trying to run a dos command